A key focus of my blog is Science, Technology, Engineering and Mathematics (STEM). I key component of medicine is toxicology which has both clinical and research aspects. If you’re on the clinical testing side, there are certain principles involved. The following guest post is entitled, 4 Principles of Toxicology Testing in Clinical Labs.
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Toxicology testing in clinical laboratories is essential for monitoring and evaluating the impact of toxic substances on human health. It plays a crucial role in helping us understand how our environment affects us and providing information to healthcare professionals about possible risk factors associated with specific exposures. The four principles of toxicology testing provide vital insight into the practice of toxicology testing.
1. Collection
The first step in any toxicology test is collecting a sample from the tested person. This can be done using various methods, such as blood or urine sampling. In some cases, tissue samples may also be necessary for more specific tests. Depending on the type of sample being collected, additional steps may need to be taken to ensure that the sample is adequately preserved and handled.
Once the sample is collected, healthcare professionals must test it with clinical laboratory equipment and supplies. Equipment suppliers for clinical labs provide a wide range of solutions for any testing need, from test kits to specialized instruments for measuring sample toxins. These suppliers also offer a variety of consumables, such as reagents and disposables, that are essential for testing samples. In addition, they provide training and support to ensure that tests are accurate and reliable.
To get the most accurate results, it is vital to use the correct type of equipment for a given test. For example, a specialized laboratory oven might be needed for specific tests, while a microscope might be necessary for others. Knowing what equipment is required can help ensure accurate testing and results.
2. Analysis
Once the sample has been collected, it must then be analyzed to determine what substances are present and how much of each substance exists in the sample. This can be done through various tests, such as chromatography or spectrophotometry. The results from these tests will indicate which specific chemicals or other elements are present in the sample.
The analytical techniques used to analyze the sample can vary depending on what it is being tested for. For example, if a sample is being tested for pollutants, then methods such as fluorescence spectroscopy may be employed. This technique measures the amount of light absorbed by different substances to identify them. Similarly, gas chromatography may be used to analyze samples for volatile compounds. This technique separates the components of a sample based on their boiling points and allows for highly accurate quantification of them.
Once the results from the analytical techniques have been obtained, these can then be compared to various standards to determine if any issues are present with contamination. Standards may vary across different jurisdictions, depending on the regulations in place. For example, if a sample is being analyzed for heavy metals, the results must compare to the accepted levels set by environmental protection agencies. It is essential to ensure that any substances present in a sample are within acceptable limits so as not to pose a risk to health or the environment.
3. Interpretation
Interpreting test results is essential for determining if any health risks associated with specific exposures exist. Toxicologists use various techniques to assess the toxicity of the substances found in a sample. This includes looking at the amount of each substance present and its potential effects on humans or animals.
Several factors must be considered to interpret a sample test’s results accurately. Factors such as the dose-response relationship, environmental fate, and bioavailability should all be examined. Additionally, healthcare professionals must consider potential synergistic effects to understand the full implications of the test results.
The dose-response relationship is an essential factor to consider when interpreting toxicity test results. This relationship describes the rate at which exposure to a substance increases or decreases its associated health risks and can be used to determine if specific exposures are safe or not. Environmental fate refers to how long a substance persists in a particular environment. At the same time, bioavailability describes the amount of a substance that enters the body and the rate at which it is absorbed.
Synergistic effects refer to interactions between substances that can cause adverse health effects. For example, exposure to low levels of two chemicals may not result in any adverse effects individually, but when combined, could lead to serious health risks. Toxicologists must consider these factors when interpreting test results to ensure accurate and comprehensive interpretation.
4. Communication
Once the results from a toxicology test have been interpreted, it is essential to communicate any findings to those involved in the testing process. This includes notifying healthcare providers about any significant health risks associated with exposures to certain substances, as well as informing laboratory personnel about how to handle any hazardous materials present in samples properly. Additionally, communication between different laboratories may be necessary when coordinating multiple tests related to the same exposure event.
When communicating results to healthcare providers or laboratory personnel, it is vital to be clear and concise. The report should include all relevant information and recommendations for further action or follow-up testing. The report should also be backed up by documentation such as case history forms or chemical analysis reports ensuring accuracy. Healthcare professionals should also provide reference materials to facilitate further understanding.
Before disseminating any results, it is essential to review the material for accuracy and completeness. Quality assurance procedures should be followed to confirm that all necessary steps have been taken before disseminating information. Relevant personnel should also be consulted where possible, as this can help identify potential issues or discrepancies.
In Summary
The principles outlined here provide an overview of the various steps involved in toxicology testing and how they all work together to keep individuals safe from adverse health effects associated with exposure to hazardous materials. By following these guidelines, clinical laboratories can play a vital role in keeping patients informed and protected from potential risks.
The first principle of my blog is “Creating Ecosystems of Success”, and one of the main focuses of my blog is awareness of the Science, Technology, Engineering, and Mathematics (STEM) careers and fields. Up to this point I’ve written several posts discussing the ‘Biomedical Sciences’ which I’ve been trained in: Pharmacology, Toxicology, ADME/Drug Metabolism, and Inhalation Toxicology. In this post I want to discuss what “Regulatory Science” and “Regulatory Affairs” are – the scientific interface between the ‘Public’ and ‘Private’ sectors where the safety of commercial products sold to the general public are determined – a science not well understood by the general public despite its importance to our everyday lives – myself included initially.
“You can always go into ‘Regulatory’,” a classmate who I’ll refer to as Greg said, during graduate school at the University of Michigan. I was feeling the stress of working on my thesis project which consisted entirely of ‘Bench’ or ‘Basic’ scientific research, and lamenting that I wasn’t sure if I wanted to stay in academia once I finished my dissertation. Greg had worked in one of the bigger Pharmaceutical companies, and understood everything that comprised them. At the time I wanted a career with a ‘regular’ schedule which is something I’ll describe more in depth in my next blog post which will discuss the ‘Basic Sciences’. I, coincidentally, did start a career as a Regulatory Scientist by accident, depending on your belief system.
When giving my annual Toxicology lecture at SUNY Albany, I always tell the class that Regulatory Scientists are ‘Watch Dogs’ or ‘Gate Keepers’ who evaluate new products generated by the ‘Private Sector’ to make sure they are safe for the public. What types of products am I talking about? You can start with anything in and around your home, whether it be food products, pharmaceuticals, or industrial chemicals, air fresheners, household cleaners, paints, or cosmetics. These are just the chemicals which we consume, or are exposed to on a personal level. Another context is the environment. For every product generated, questions must be asked about what that product will do to wildlife, their unique ecosystems, lakes, oceans, the air, etc. Here think about coal and petroleum products as good examples.
The term ‘Regulatory’ is rooted in the ‘Regulations’ put in place by Federal and State governments – laws and statutes which dictate how and when the government should act in the general public’s best interests to ensure that the products they are being sold are safe. Going back to the previous paragraph, there are regulations for example for registering the following: crops and commodities, livestock and poultry, pharmaceuticals, medical devices, industrial chemicals, industrial materials and textiles, and energy products such as petroleum and coal. We’re very close to the use of ‘Nanomaterials’, so products that contain them are of particular interest now.
Here is a good place to think back to the 2016 Presidential election where the then candidate, Donald J. Trump, discussed the need to rollback excessive, costly and burdensome regulations put in place by the Obama administration to allow private businesses to grow and thrive. Having an understanding of Regulatory Science and Regulatory Affairs is the essence of that discussion because it takes resources to demonstrate the safety of products; otherwise it can cut into profits if their uses are restricted. Important questions to thus consider are: 1) is there such a thing as over-regulation; and 2) is there a happy balance between business and keeping the public and environment safe? Some food for thought.
Regulatory Scientists work in both Public and Private sectors. On both sides each must understand the Federal and State government laws and regulations. Scientists in the Private sector must understand the regulations and provide the government with the data it needs so that their companies can efficiently register their products. Scientists in the Public sector must understand the regulations to ensure that the companies trying to register their products are in compliance, so as to not cause injury to individuals in the general public and create subsequent litigation. While this post is about Regulatory Science, it’s also worth noting here that most of the private companies also have scientists working in the ‘Applied Sciences’ and ‘Research and Development’, which is where their new products come from – examples are the Food, Pharmaceutical, Biotech, and Crop-Science companies.
Where do Regulatory Scientists receive their training and what types of skills do they need? Most Regulatory Scientists receive their training in the ‘Basic Sciences’ at major research universities, such as the University of Michigan, where I received my training. This means that they first become trained in specific scientific areas of expertise – Pharmacology and Inhalation Toxicology in my case – and they then use those knowledge sets in the Regulatory world to make safety decisions. The same is true for the Applied Sciences where that expertise is used to create new products. As you can see these worlds are closely interrelated.
The four Biomedical Sciences I’ve discussed in detail – Pharmacology, Toxicology, ADME/Drug Metabolism and Inhalation Toxicology – are all basic sciences which translate to the Applied Science and Regulatory sciences. Scientists trained in these fields and others can either remain in academia, or take their skill sets into the Public or Private sectors. See my post entitled, “The transferrable skills from a doctoral degree in the basic sciences” to get a feel for what skills are necessary to work in the Regulatory Sector or Regulatory Affairs. Just briefly, a couple are of the skills are the ability to: 1) work on teams; 2) write; 3) plan; and 4) speak orally, as there are lots and lots of meetings.
There are typically two contexts for Regulatory Science – one which takes place in a classic laboratory setting, and the other which takes place in an office setting. In the lab setting, experiments are carried out to test products safety. In the government office setting, scientists interpret the results generated on specific products using the above-mentioned regulations and policies which each scientist has to learn when starting in the field. It’s worth noting here that science is constantly changing and evolving, and thus a challenge to working in the Regulatory sector in government settings is staying current on new and relevant scientific breakthroughs and methods. This can be done in any number of ways including attending national meetings, and participating in special ‘work groups’, for example.
A third context for Regulatory Science is consulting. Many scientists, after working in the Public or Private sectors, eventually opt to the start their own consulting companies. These consulting groups typically work with Private sector companies to get their products registered swiftly and efficiently, with the goal of keeping their costs as low as possible.
What do Regulatory Scientists make in terms of salary? That is in part dictated by one’s degree level, and whether the scientist works in the Public or Private sectors. Scientists in both sectors can start out making $70,000. Federal and State Regulatory Scientists are typically paid according to the ‘General Schedule’. While Regulatory Scientists in Private Industry are paid according to what that company determines the individual is worth, and the mutually agreed upon salary.
In closing, when you think about Regulatory Science, think globally. While the United States Government has numerous agencies to protect the general public – the EPA, FDA, USDA and the NRC to name a few – other countries around the world have them as well. And there are actually global partnerships and cooperatives amongst nations which are important when it comes to international trade and commerce, in addition to environmental protection. A career in Regulatory Science thus has the potential to touch not only the lives of those in your immediate circle, but also those in faraway places.
The next posts in this series will talk about what Basic Research and Science are, and then my personal journey towards becoming a Scientist. If you enjoyed this post you may also enjoy:
If you’ve found value here and think it would benefit others, please share it and/or leave a comment. To receive all of the most up to date content from the Big Words Blog Site, subscribe using the subscription box in the right hand column in this post and throughout the site. Please visit my YouTube channel entitled, Big Discussions76. You can follow me on the Big Words Blog Site Facebook page, and Twitter at @BWArePowerful. Lastly, you can follow me on Instagram at @anwaryusef76. While my main areas of focus are Education, STEM and Financial Literacy, there are other blogs/sites I endorse which can be found on that particular page of my site.
“While other bodily tissues can tolerate varying degrees of O2 deprivation, it is well understood that even short periods of deprivation of the brain can cause irreversible damage, unlike with long periods of food and water deprivation.”
With the exception of my Blockchain Technology post, my previous Science, Technology, Engineering and Mathematics (STEM) posts have covered the fields of: Pharmacology, Toxicology, and ADME/Drug Metabolism – all of which are considered ‘Biomedical’ sciences. Similar to those fields, Inhalation Toxicology as a discipline dates back to over a century ago, and is very complex regarding the wealth and depth of information available. It’s also still evolving today.
The goal of this post is not to address every detail and nuance of the field, but instead to give readers unfamiliar with it a basic introductory understanding of the discipline. This post was prepared for a general audience and thus any fellow Inhalation Toxicologists who may read this, may find it a little too simplistic. That’s okay though, as the goal is to educate others on our field and what we do. Further details about the many aspects of Inhalation Toxicology can be accessed online, or in scientific journals.
This overview of Inhalation Toxicology definitely falls under my principle of ‘Creating Ecosystems of Success’ as it is a very unique knowledge and skill set possessed by only a select few – one of which I acquired accidentally when seeking training in ADME/Drug Metabolism as a ‘Postdoctoral’ scientist. Why is Inhalation Toxicology a unique skill set? I’ll start with a holistic discussion about the three routes of human exposure which will take us briefly into another biomedical discipline; ‘Anatomy and Physiology’, which deals exclusively with the organ systems within the human body, and how they collectively work together at the tissue and cellular levels.
Routes of Exposure
My posts regarding Pharmacology, Toxicology, and ADME/Drug Metabolism focused on exposure to chemicals primarily through the oral route – ingestion through the mouth and then absorption into the ‘Gastrointestinal Tract’ (GI-Tract). While we typically think about the ingestion of chemicals through the oral route, the reality is that humans can be exposed to drugs and toxicants through two other routes; the dermal route by way of our skin, and the inhalation route by way of our ‘Respiratory Tracts’ – the region spanning from our nasal passage down into our lungs where gas exchange with the atmosphere occurs. Each route has its own unique properties anatomically which impact the potential absorption of chemicals into the body where they can exert their therapeutic or toxic effects at specific tissues.
Each route receives differing amounts of what’s called the ‘Cardiac Output’ or the blood delivered from the heart. On average, the GI-Tract receives 21%, the skin receives 9%, and the lungs receive 100% of the heart’s Cardiac Output. This makes sense as the function of the lungs is to facilitate gas exchange between our bodies and the Earth’s atmosphere.
The Alveoli and Gas Exchange
The lung’s ‘Alveoli’ are critical for the body’s absorption of ‘Molecular Oxygen’ (O2) into the bloodstream. Once inhaled, the O2 in the air is very rapidly absorbed into the pulmonary capillaries from the alveolar spaces where it binds to the ‘Hemoglobin’ in our blood while the ‘Carbon Dioxide’ (CO2) releases into the alveolar spaces to be exhaled. This exchange of O2 and CO2 are both very rapid and efficient in healthy lungs – something our bodies do without us even thinking about it. What allows for this very efficient exchange of gases with the environment is a very, very thin 0.5 micron three-cell layer separating the alveolar spaces from our pulmonary capillaries. These capillaries immediately receive and return blood to the heart for distribution to the body.
Without the continuous exchange of O2 and CO2 through our lung’s alveoli, our bodies could not function as O2 is a necessary substrate for our body’s many tissues at the cellular and molecular levels. This is important because while other bodily tissues can tolerate varying degrees of O2 deprivation, it is well understood that even short periods of deprivation of the brain can cause irreversible damage, unlike with long periods of food and water deprivation. For this reason alone, maintenance of proper respiratory function is critical. With that, I’ll transition into what Inhalation Toxicology is and why it’s important.
Hazard Through Inhalation
Inhalation Toxicology is the study of the harmful effects of chemicals on living systems through the inhalation route of exposure via breathing – typically as it applies to mammalian species. It’s a very important field as respiration is a critical biological process for mammals as described above, and thus any toxicant that compromises the body’s capacity to exchange O2 and CO2 with the environment is very dangerous.
Before I discuss the types of chemical agents that can cause injury through inhalation exposure, I’ll first describe the two types of effects that can result from exposure to inhalation toxicants; ‘Portal of Entry’ effects and ‘Systemic’ effects. A Portal of Entry (POE) effect is an effect produced in the tissue or organ of first contact with a chemical or toxicant. In this case it’s an effect where a toxicant causes damage starting from the nasal passage down into the multiple regions of the lung. There are multiple regions and cell-types along the respiratory tract – each with specific functions – all of which can be uniquely injured.
In laboratory settings described later, some POEs are instant when observing lab animals and manifest as ‘clinical signs’ which are visible. Irritation in the respiratory tract can trigger the ‘Paintal’ reflexes and ‘Bradypnea’ in rodents which are immediate changes in the breathing patterns of the animals through very sensitive nerve processes and receptors in respiratory tissues. Anyone who has worked in a research lab and has opened a bottle of concentrated Hydrochloric Acid outside of a fume hood appreciates how quickly irritation can occur, as it only takes seconds to feel the burning sensation in the nose followed by: coughing, watering eyes, shortness of breath, etc.
Long-Term Effects
Other POE Effects are more time dependent and can take hours, days, or weeks to fully set in. Some are some are reversible, while others are irreversible. Prolonged exposure to some toxicants can cause ‘Inflammation’ in the lungs leading to ‘Pulmonary Fibrosis’ (formation of scar tissue) or the formation of ‘Pulmonary Edema’ – both of which compromise lung function and can eventually be fatal. ‘Asbestos’ poisoning causes injury through prolonged activation of the ‘Immune’ system in the lungs, damaging them over time as the Asbestos particles cannot be removed once inhaled.
Smoking cigarettes is a good example of people willingly injuring their lungs. The paper used to roll cigarettes and the ‘Tobacco’ inside them contain thousands upon thousands of compounds before the cigarette is even ignited. Once lit and those chemicals are ‘combusted’, they transform into numerous other chemicals – some of which are referred to as ‘Reactive Intermediates’ which themselves come into contact with the cells of the Respiratory Tract. Years and years of direct cigarette smoke inhalation can cause irreversible damage leading to diseases like Lung Cancer. There is also risk of lung injury from living in industrial areas where there is the potential to inhale combusted compounds and particulates from factory emissions.
Before moving on, I’ll add here that while many inhalation toxicologists consider the lung itself to be the most important part of the Respiratory Tract, recent science has shown that the Nasal Passage is also a toxicologically revelation tissue as it relates to inhalation exposure. It contains drug metabolizing enzymes similar to those described in my ADME/Drug Metabolism post. The lungs do as well. Some chemicals can thus damage these regions if inhaled for prolonged periods of time.
Systemic Effects
Systemic effects refer to injury/toxicity in other parts of the body beyond the Respiratory Tract. If a chemical/toxicant can efficiently pass through the lung’s alveoli as described earlier, it can enter the blood stream and into the body’s general circulation. From there it can damage other organs as discussed in my Toxicology post. Medicinally, some therapeutics such as anesthetics for surgeries are actually administered this way – Halothane is an example.
Two classic systemic inhalation toxicants are Carbon Monoxide (CO) and Hydrogen Cyanide (HCN) which I’ve hyperlinked in case you’re curious to learn more about how they work. While CO poisoning has been associated with accidental deaths from tailpipe emissions in garages, HCN is a known potential chemical weapon which is particularly dangerous in enclosed spaces such as subway stations – something our intelligence agencies are very aware of.
These are just a few examples of toxicity through the inhalation route of exposure. There are many other chemicals and substances that can cause injury and in some cases therapeutic benefit through the inhalation route of exposure. Many industries and groups highly consider Inhalation Toxicology. They include:
• The Chemical Industry: Pretty much any industrial chemical that’s generated has the potential for inhalation exposure depending on its ‘Physical-Chemical’ properties, and how it’s used. These include paints, pesticides, and disinfectants – any product that companies are looking to sell to the general public. • The Tobacco Industry: The Tobacco Industry has to have a firm understanding of what cigarette smoke does to its customers and bystanders inhaling ‘second hand’ smoke. They are thus very interested in the long-term effects of cigarette smoke inhalation. • Nanoparticles and Nanomaterials: We’re very early in the use of ‘Nanomaterials’, and there is a lot that is unknown regarding the toxicity of these particles – in this instance, when they’re inhaled. • National Defense: Our military and the ‘Defense’ sector very much care about Inhalation Toxicology as soldiers are sometimes sent into theaters of war where enemies use biological and/or chemical weapons. There are also unfortunate incidences where chemical weapons are unleashed on civilians such as the recent chemical attack in Syria where rescue officials believe the agent used was Chlorine gas. • The Pharmaceutical Industry and Medical Devices: Some medicines can and must be delivered through the inhalation route. A classic example is the use of ‘Albuterol’ for patients with Asthma, but there are numerous other examples such as when anesthetics and other treatments are given through inhalation exposure. • Public Health: Federal and State governments, academic researchers and private sector companies are always cognizant of how the general public is exposed and affected by any of the chemicals described above which invariably end up in the air, and can cause any number of disease states including Asthma, and in some cases Lung Cancer.
Inhalation Toxicology Research
Having introduced the field in terms of background and context, I’ll now discuss some of its experimental and technical aspects using visuals provided by CH Technologies – a leading company in the manufacture of Inhalation Toxicology exposure systems. Inhalation Toxicologists and Scientists not only need an understanding of the biology of injury to the Respiratory Tract via inhalation exposure (examples described above), but they also need an understanding of how to properly create the experimental conditions to test for inhalation toxicity. It’s relatively straight forward to feed a test specimen the chemical of interest in food or water, or to apply it via the skin, but how do you administer it for inhalation exposure?
The answer is that the chemical must be administered as a ‘gas’, an aerosol’, a ‘dust’, or even a ‘cigarette smoke‘ suspension in some instances. This involves some knowledge of Chemistry and Physics, as well as Mathematics and Statistics. A key aspect of any toxicological field is proving the concentration/dose tested and properly correlating it with the effects observed. Scientists must thus be able to verify their test atmospheres, and there are numerous ‘analytical’ chemical methods for doing so.
Gases, Aerosols, Dusts and Vapors
Some chemicals readily exist in the ‘Gas Phase’ – that is they have what is referred to as a high ‘Vapor Pressure’ and are very ‘Volatile’. Some are liquids while others are solids. Mothballs are an example of a volatile substance – a solid which ‘sublimes’ and converts directly into a vapor. They give off the unique odor most of us know from our grandparents’ closets, and are comprised of the chemical ‘Naphthalene’ which itself has a high vapor pressure. Other chemicals have low vapor pressures and are considered ‘Non-Volatile’ and must form aerosols to be inhaled – think of a mist from a spray bottle. ‘Dust’ suspensions can be generated as well for experiments. In some instances, generating inhalable suspensions are not feasible depending on the properties of the test material of interest.
Test Models and Species
While the test species for Inhalation Toxicology studies vary, the species of choice is typically rodents – rats and mice. In some instances guinea pigs and primates are used. Each of these species possess the same organs that humans possess for the most part, and are thus useful models for human exposure. Scientists must be well trained in both caring for the test animals and also operating the highly specialized equipment used in these studies which I’ll cover next.
Test Systems
Testing a drug’s/chemical’s efficacy/toxicity through inhalation exposure requires the use of an ‘exposure chamber’ where an inhalable atmosphere of the test article is generated for inhalation exposure by the test subjects. The accompanying picture shows a single level chamber with the accessory equipment used for measuring the chamber’s inner atmosphere using some of its ‘exposure ports’. Click on the image to enlarge it. Using the accessory equipment, the concentration of the test material in the chamber can be monitored by the scientists running the experiment, in addition to other important measurements including: O2, CO2, temperature and humidity to name a few.
To generate the chamber’s test atmosphere, most modern systems utilize an air-pressure pump to create an in “inflow” into the exposure chamber, and a vacuum pump to create an “outflow” from the chamber – together creating a consistent supply of O2, and removal of CO2 for the test subjects. The accompanying diagram shows a complete inhalation exposure system designed to expose the test subjects to aerosols. Click the image to enlarge it. Whether gases, aerosols or dusts are generated, a supply-line for the test article is ligated into the air supply line feeding the exposure chamber, allowing for the control of the concentration within the chamber by the scientist – something that must be actively monitored throughout experiments.
Whole-Body and Nose Only Exposures
Inhalation studies can use ‘whole-body’ chambers where the animal’s whole body is exposed, or ‘nose- or head-only’ chambers which in some instances have become the preferred method due to their increased specificity to the respiratory tract. A potential drawback of using Whole-Body chambers is that test subjects – usually rodents in the process of grooming themselves can orally ingest the test material by licking their fur coats. ‘Dead space’ within whole body chambers is also a drawback. The accompanying picture shows how a rodent sits in a ‘restraint‘ tube during exposure. An important key to properly running inhalation exposure experiments, is making sure that animals are adequately acclimated to the tubes and are comfortable in them for extended periods of time.
The accompanying photograph shows a Nose-Only inhalation exposure chamber with all of its exposure ports occupied by the restraint tubes for rodent species. Click on the image to enlarge it. The picture further shows how the number of animals exposed can be increased by stacking multiple chamber levels and increasing the total number of exposure ports.
Depending on the questions being asked in that particular experiment, exposures can range from: hours, to days, to weeks, to months and years. During and afterwards, any number of toxic or therapeutic biological responses can be measured including changes in: clinical signs, body weights, blood chemistry, clinical chemical parameters, and changes in organ weights and tissue microstructure (histopathology). Again, collectively these are a very technical set of experiments to run, and which require a very specific and unique skill set.
Inhalation Toxicology Training
How can students get trained in Inhalation Toxicology? Beyond high school, students can major in Biology, Chemistry, or any of the Biomedical sciences as undergraduates where they can start receiving lab training if there are researchers at that particular university, or one close by. Further training can be obtained at the Masters or Ph.D. levels. Similar to Pharmacologists, Toxicologists and Drug Metabolism Scientists, Inhalation Toxicologists generally receive their training at major research universities.
As a sub-discipline of Toxicology, scientists looking to receive training in Inhalation Toxicology can have varying backgrounds in terms of degrees conferred. If an individual doesn’t initially train in an Inhalation Toxicology lab, they can work in these labs as Postdoctoral scientists or ‘Fellows’ with any of the Biomedical degrees, and even with ‘Medical’ and ‘Veterinary’ degrees. When I gained my training in Inhalation Toxicology, my Ph.D. was actually in Pharmacology.
Depending on the degree level earned and where the scientist is employed, Inhalation Toxicologists can earn starting salaries of $60,000-$70,000 and above. One of the themes of my posts in this series is there is a tremendous amount of flexibility and overlap in the Biomedical sciences. Upon receiving training in Inhalation Toxicology, scientists must then determine which sector they want to pursue – academia, the private or public sectors, or nontraditional careers. Scientists with this background also have the flexibility to combine their knowledge sets with other disciplines to go into a wide variety of areas in: pharmaceutical companies and biotechs, chemical companies, consulting, patent law and even starting their own companies and ‘Contract’ labs.
Toxicology For the 21st Century
It’s worth reiterating something from my Toxicology blog post and that is there’s an effort currently underway called ‘Tox-21’ or ‘Toxicology For the 21st Century’. One of the goals for Tox-21 is to minimize animal usage. Currently, there are efforts to develop methods to test for inhalation toxicity using in vitro models and cell culture preparations simulating animal tissues. Students interested in this field will position themselves well by learning about some of these advances that are on the horizon.
Thank you for taking the time to read this post, and I hope I was able to shed some light onto what Inhalation Toxicology is as a field. Similar to the other disciplines I’ve discussed, Inhalation Toxicologists have their own professional societies and meetings. While the Society of Toxicology has subsections on Inhalation Toxicology, the field has two of its own professional societies and meetings; the American Thoracic Society, and the American Heart Association as the Heart is a major organ affected by the inhalation of toxins.
The next posts in this series will talk about what Regulatory Science is, and then my personal journey towards becoming a Scientist. If you enjoyed this post you may also enjoy:
A special thank you is extended to my Postdoctoral Advisor and his lab for allowing me to learn and train in this exciting field. I also want to thank two other colleagues who will remain anonymous – very brilliant veteran inhalation toxicologists with vast experiences, who have continued to teach me about the field. Finally, I want to thank and acknowledge CH Technologies for graciously answering my many phone calls as a Postdoctoral Scientist when I was first learning how to use their inhalation systems; and also for graciously providing the diagrams and pictures of the inhalation exposure chambers, and systems used in this post.
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Similar to Pharmacology, the field of Toxicology is centuries old and is very complex regarding the wealth and depth of information available. It is also still evolving today. The goal of this post is not to address every detail of the field, but instead to give readers a basic introductory understanding of the discipline. Further details about the many aspects of Toxicology can be accessed online, or in scientific journals.
When I meet people outside of my scientific circles at career and STEM fairs, Toxicology doesn’t get confused with other disciplines the way Pharmacology and Pharmacy do – I thus won’t open with a story about misunderstandings. I’ll simply say that Toxicology an exciting field with vast opportunities for individuals who are trained in it. Following my principle of “Creating Ecosystems of Success”, I wanted to write an overview of the field – particularly for parents and young students who have an aptitude for science and may be interested in Toxicology as a career one day. As you’ll see later on, Toxicology is an important component of numerous industries, and scientists with this training will never be without jobs.
Doses and Poisons: Paracelsus’ Riddle
“The dose makes the poison,” is the popular toxicology adage credited to the Swiss physician and alchemist Paracelsus. Simply put, given the proper dose, even chemicals and substances considered harmless can be poisonous – too much sugar or water for example. Dosage or the amount of a substance one is exposed to is a key component of Toxicology – keep this in mind as you read through this post. Also keep in mind the route of exposure. Toxicologists are always considering that an individual can be poisoned through oral ingestion, or through either dermal or inhalation exposures.
I think of Pharmacology and Toxicology as “sister” sciences – both dealing with the effects of xenobiotics on living systems. While Pharmacology focuses more on the therapeutic effects of xenobiotics, Toxicology focuses on the harmful effects – in most cases humans but in some instances other mammalian and non-mammalian species. These effects can occur on the molecular, cellular, tissue, and whole organism levels. While Pharmacology and Toxicology are separate disciplines, they have several overlapping principles and skill sets allowing individuals credentialed in one to work in the other.
Toxicology and Drugs
I’ll start my discussion of why Toxicology is important with drugs. Both biotechnology and large pharmaceutical compan9ies have to understand and report a drug’s toxicological profile to the federal government before selling it to the general public. Many promising drugs actually never make it to market because they’re too toxic. Some actually make it and are then recalled – Rezulin for example.
There are also both clinical and research contexts for Toxicology. Similar to Pharmacology, all medical practitioners (Anesthesiologists, Physicians, Pharmacists, Nurses, Surgeons, etc.) must receive some toxicology training as they all need an understanding of the potential toxicities of the drugs they’ll ultimately prescribe. They need to understand how much of a given pharmaceutical will be beneficial vs. harmful to patient – a drug’s “Therapeutic Index”. If the patient is taking multiple medications, “Drug-Drug” interactions can result – toxicities and side effects resulting from one or more drugs being present in the body at the same time causing others be poisonous. The patient’s current liver and kidney function are critical here as well as they will ultimately determine how long the drugs persist in the body. In an emergency room, physicians must often determine what a patient may have been poisoned by in order make swift life-saving decisions.
Forensic Toxicologists are instrumental in solving crimes and deaths. They’re masters of detecting chemicals in the body’s tissues and understanding how they may have led to a victim’s death. Michael Jackson’s overdose on “Propofol” comes to mind, and is just one of many examples.
Toxicology in Research Settings
In the research context, think about experimentation in laboratory settings – well designed studies run by scientists asking questions and looking for specific answers. Initial toxicological studies typically involve determining how a toxicant exerts its effect on the molecular and then on the tissue/organ levels – similar to how Pharmacologists identify new drug targets. After determining a toxicant’s molecular mechanism, there is then the need to determine the toxic dose range of the chemical at the molecular, tissue and whole animal levels. This is called a “Dose Response” – a critical tool of both Pharmacology and Toxicology where scientists look to determine if increasing the amount of the chemical in question, increases the amount of biological response. This applies to a broad spectrum of chemicals – pharmaceuticals and industrial chemicals alike.
What am I referring to when I say industrial chemicals? Simply look around your home at all of the products you use daily including: household cleaners, cosmetics, pesticides (Raid for example), and even additives and preservatives in some the foods we consume. Thus when you think about Toxicology, think very broad in terms of scope. For this reason, individuals with toxicology training will never be without jobs as everything we use must be screened for safety. Toxicologists are currently in high demand.
Sub-Disciplines of Toxicology
Similar to Pharmacology, there are numerous sub-disciplines within Toxicology. The following is a list of some of the major areas beyond what’s been described thus far. These areas are heavily considered by government agencies and private sector companies who all need toxicologists to create new products, determine the safety of those products, and lastly determine the fate of those products once used:
Aquatic, Eco- and Environmental Toxicology: While these are distinct disciplines all in themselves, I’ve grouped them together for simplicity. They collectively consider toxicity to non-human life – aquatic, avian, other terrestrial life. They consider what happens to ecosystems if a particular species is inadvertently killed off. Some questions involve where the toxicant goes in our environment, how long it stays there, and if it breaks down into something else more or less toxic.
Computational (In silico) Toxicology: Uses computational models, to predict mammalian toxicities. “Tox21” is a current effort to minimize animal testing using computational and predictive models.
Entomotoxicology: Determines how a given chemical is toxic to insect species. This is very important for the creation of pesticides, and it’s also critical for Ecotoxicology as the chemical designed to control specific insects may easily kill something else unintended.
Food Safety Toxicology: Looks at the potential toxicity of man-made or natural ingredients intentionally added to our food. Heat formed compounds are of particular concern – acrylamide and furan are examples which can spontaneously form during the cooking of certain precursor molecules. Lastly the ingredients in food packaging are also considered as they can be ingested through the foods they are in contact with.
Forensic Toxicology: As described above, deals with the solving of crimes – often determining what a victim was poisoned with.
In vitro Toxicology: Characterizes how a toxicant works using cell models and protein systems as opposed to whole animals.
Mammalian Toxicology: Studies the effects of a given toxicant on mammalian systems – traditionally using animals to model to human toxicity. Experiments can be designed over multiple dose ranges and through any of the three routes of exposure – oral, dermal or inhalation. Time of these studies can range from hours to days, to years. Varying indices can be studied such as life-stage sensitivity, cancer potential, or the ability to inhibit one’s immune response. Mammalian toxicology is very important in “Regulatory” settings described below.
Modes of toxic action: Characterizes how toxicants exert their action on the molecular, cellular and whole animal levels. This information can be used to design chemicals to control something like a pest, or to determine how a cancer tumor-type forms.
Medical Toxicology: As described above, deals with the prevention of patient poisoning in medical settings.
Occupational Toxicology: Involves potential toxicity to workers who are in contact with a given toxicant and may get exposed through their skin or through inhalation.
Regulatory Toxicology (Private Sector): When the private sector creates a product, it must work with federal and state government agencies to determine the safety of that product. The products can be: drugs, pesticides, cosmetics, food additives, paints – you name it. Regulatory Toxicologists in the private sector must understand government laws and guidelines for the products they’re creating – knowing which animal and in vitro studies to run to get their product registered in the most cost efficient way.
Regulatory Toxicology (Public Sector): Involves government and state agencies determining the safety of products produced by private industry. This usually consists of considering real world human exposures, and looking at any pertinent data (animal, in vitro, exposure or physical chemical) that might help model those exposures to determine levels of safety or lack thereof.
Toxicogenomics: Similar to Pharmacogenomics, looks at the genetics unique to individuals to determine potential increased toxicity for that individual.
Toxinology: Deals specifically with animal, plant and microbial toxins.
Toxicokinetics: Similar to the description in my Pharmacology post, Toxicokinetics deals with how the body handles toxicants in terms of absorption (entry to the body), tissue accumulation (distribution), biotransformation (metabolism) of the molecule, and excretion (elimination). I will revisit Pharmacokinetics and Toxicokinetics in greater detail in a separate post.
Toxicology Careers and Training
So have I convinced you that toxicologists are literally everywhere? Similar to pharmacologists, toxicologists can leverage their skill sets to work in other capacities besides academia, and the public and private sectors. When combined with other fields such as law and business, toxicologists can start their own companies – consulting for example, and in some cases they can create new health-related technologies and innovations.
Depending on the degree level earned and where the scientist is employed, Pharmacologists can start earn starting salaries of $60,000-$70,000. There are numerous avenues by which to pursue training in Toxicology. According the website of the Society of Toxicology, training can start as early as high school and the amount of training one pursues (Bachelors, Masters, Ph.D.) will depend upon specific career goals. As there is tremendous overlap in skill sets of scientists in the biomedical sciences, one need not have a degree in “Toxicology” per se to work in the field in most cases. An exception is the federal government which is very stringent in terms of matching one’s academic credentials exactly with job openings regardless of one’s actual scientific training and expertise. An individual for example with a Masters or Ph.D. in another biological science, MD, or a DVM for example can receive training in Toxicology through postdoctoral fellowship.
Certifications in Toxicology and the Society of Toxicology
Toxicology also has a unique certification – the Diplomate of the American Board of Toxicology (DABT). Earning one’s DABT allows toxicologists to be nationally certified which is particularly important in the private sector, and in capacities such as serving as expert witnesses in litigations. The European Union has a similar certification titled “European Registered Toxicologists” (ERT).
If you are interested in learning more about the exciting field of Toxicology, I suggest that you visit the website of the Society of Toxicology (SOT) – the major professional society for Toxicology. Click on the “Careers” tab and scroll down to the “Becoming a Toxicologist” tab. A wealth of information is available talking about numerous aspects of the field. Similar to Pharmacology, Toxicology has its own annual meeting hosted by SOT where scientists gather to network, discuss their results, employers seek new job prospects, and companies show their latest devices and technologies.
Thank you for taking the time to read this post, and I hope I was able to shed some light onto what Toxicology is. If you enjoyed this post, you might also enjoy:
A special thank you is also extended to Dr. Chester Rodriguez for his contribution to this post, and sharing the importance of earning one’s DABT.
The Big Words LLC Newsletter
For the next phase of my writing journey, I’m starting a monthly newsletter for my writing and video content creation company, the Big Words LLC. In it, I plan to share inspirational words, pieces from this blog and my writers blog, and select videos from my four YouTube channels. Finally, I will share updates for my book project The Engineers: A Western New York Basketball Story. Your personal information and privacy will be protected. Click this link and register using the sign-up button at the bottom of the announcement. If there is some issue signing up using the link provided, you can also email me at bwllcnl@gmail.com . Best Regards.
The field of Pharmacology is centuries old and it is very complex with respect to the wealth and depth of information available. It is still evolving today. The goal of this post is not to address every detail of the field, but instead to give readers a basic introductory understanding of the discipline. Further details about the many aspects of Pharmacology can be accessed online, or in scientific journals.
I earned my Ph.D. in Pharmacology from the University of Michigan. I admittedly didn’t understand the field initially, although I did know that it dealt with drugs and hoped that a degree in it would one day secure a position for me in the Pharmaceutical industry. Since starting my studies in 1999, completing my degree in 2005, and starting my current career as a Regulatory Scientist, I’ve gotten the same question over and over again, “You have a background in Pharmacology? Are you a Pharmacist?” At Career and STEM Fairs, I get this question a lot, and thus following my principle of “Creating Ecosystems of Success“, I wanted to write a brief overview of the field – particularly for parents and young students who have an aptitude for science and may be interested in Pharmacology as a career one day.
Pharmacology and Pharmacy: What’s the Difference?
“Simply put, Pharmacy is the study of what drugs do to man, and Pharmacology is the study of what man does to drugs,” said one of the Cancer Pharmacology faculty in our Principles of Pharmacology course during my first year of graduate school. This statement explained in a very simple way some of the differences between the two disciplines. Pharmacy is the study of the actual drugs administered to patients as therapeutic agents and its practitioners work at various institutions including hospitals, medical centers, and drug stores – CVS for example. Pharmacists are health professionals, earn Doctor of Pharmacy degrees (Pharm Ds), are experts on medications, and are responsible for dispensing medicines. Pharmacology is a basic research science that studies the mechanisms underlying the therapeutic effects of pharmaceuticals and potential drug candidates with the goal of developing and testing of new drugs.
All medical practitioners (Anesthesiologists, Physicians, Pharmacists, Nurses, Surgeons, etc.) must take Pharmacology courses as they all need some understanding of the mechanisms of the drugs they ultimately prescribe. Pharmacologists are the actual researchers performing experiments trying to create new drugs and identify new drug targets. They further seek to characterize how mammalian systems (in most cases human although they are also involved in developing veterinary drugs) handle molecules at the molecular, cellular, tissue and whole organism levels. It’s a vast field with many areas of specialization that I’ll discuss in the remainder of this post.
Sub-Disciplines of Pharmacology
Pharmacology classically can be divided into two parts; Pharmacokinetics, which deals with how the drug is absorbed and eliminated by the body, and Pharmacodynamics, which deals with how the drug exerts its medicinal effect mechanistically. The following sub-disciplines within Pharmacology generally fall under one of these two umbrellas or, in most cases, are a mixture of the two. Each of us or someone we know has taken a drug or a treatment which has been impacted by one of these areas. Any pharmacologist reading this can easily further parse this list out into greater detail, but again this was written for a general audience:
ADME/Drug Metabolism: Deals with how the body handles the therapeutic molecules in terms of absorption (entry to the body), tissue accumulation (distribution), biotransformation (metabolism) of the molecule, and excretion (elimination). Another focus of ADME/Drug Metabolism is “Drug Transport” which focuses on how drugs are absorbed and effluxed from cells using membrane channels and transporters impacting their effectiveness. I will revisit ADME/Drug Metabolism in greater detail in a separate post as me and some of my peers know it pretty well and find it to be a very exciting aspect of both Pharmacology and Toxicology.
Antimicrobial Pharmacology: Involves the control of bacteria, fungi, and viruses to fight off or prevent infections.
Autonomic Pharmacology: Deals with how the drug interacts with the Autonomic Nervous System (that part of the nervous system responsible for controlling bodily functions that are not consciously directed such as the heartbeat, breathing, and the digestive system) particularly through pathways involving epinephrine, norepinephrine, dopamine, and seratonin.
Cancer Pharmacology: Deals with drugs used in the treatment of cancer – usually some form of chemotherapy.
Cardiovascular Pharmacology: Deals with drugs used in treatment of heart disease and regulation of blood pressure. A well-known class is the “Statins” – cholesterol lowering drugs such as “Lipitor“.
Endocrine and Receptor Pharmacology: Deals with how a given drug binds, interacts or even blockades a given cellular receptor, and then what the receptor does or doesn’t do to impact the homeostasis of that cell or tissue. The receptor can be membrane bound or cytosolic (many hormone receptors).
Drug Discovery: Typically associated with the private sector and deals with the identification of new drug entities and the identification of new drug targets. In industry, pharmacologists generally refer to drugs as either “small molecules” which are our classic drugs like Aspirin (~180 g/mol), or “large molecules” (as heavy as 150,000 g/mol) also known as “biologics” which are generally proteins which have therapeutic effects. An example is Abbvie’s “Humira”. The units “g/mol” or grams per mole designate a chemical’s molecular weight and as you can see the size difference between the two classes is considerable.
Neuropharmacology: Similar to Autonomic Pharmacology but deals with all of the other parts of the nervous system such as pain responses – analgesics and anesthetics for example.
Pharmacogenomics: This new and exciting field looks at the genetics unique to individuals to determine the best treatments and dosages for that individual.
The Clinical and Research Sides of Pharmacology
For each of these sub-disciplines there is a clinical side and a research side. The clinical side is self-explanatory – it involves treating patients for various diseases as well as the prevention of illness by the above mentioned medical practitioners. Think of the many medications you have been prescribed when you go to see medical doctors when you’re sick or for checkups, emergencies or surgeries. But where do these medications come from originally? Also, where will new medications come from in the future?
Academic and Industrial Research
This is where the research side come comes into play. At institutions like my alma mater, and in the private sector, there are scientists working year round on research projects asking questions about current medications in addition to trying to unlock the secrets of nature to create new therapeutics. The investigations they perform involve testing molecules using whole animal models, cellular models, and in vitro systems to ask questions at the molecular level (proteins, lipids, DNA and RNA) about what the compound does. It’s this research that can get very esoteric to the general public and that is published in academic journals including: Drug Metabolism and Disposition, the Journal of Pharmaceutical and Experimental Therapeutics, and Molecular Pharmacology.
Pharmaceutical companies like Merck and Pfizer conduct research as well but instead of doing it strictly to find new knowledge, it’s to create new drugs that they can sell. The same is true for smaller Biotech companies like Biogen. Both need scientists with backgrounds in Pharmacology. The Federal Government also employs scientists with backgrounds in Pharmacology to determine the safety of new drugs before they can be prescribed to the general public. The same is true for food products and chemicals used in those products, so Pharmacologists are literally everywhere.
Careers in Pharmacology and Training
Depending on the degree level earned and where the scientist is employed, Pharmacologists can start earn starting salaries of $60,000-$70,000. Pharmacologists generally receive their training at major research universities. While undergraduates can get training in Pharmacology – nursing students for example, degrees in Pharmacology are usually conferred at the Masters and Ph.D. levels and support for the student’s educational expenses as well as a modest salary are provided. Upon attaining these degrees, scientists then determine which sector they want to pursue – academia, the private or public sectors, or nontraditional careers. With the skills obtained in graduate school, scientists with these backgrounds have the flexibility to combine their knowledge sets with other disciplines to go into a wide variety of areas in addition to drug discovery in pharmaceutical companies and biotechs including: consulting, Toxicology, patent law and even starting their own companies.
The Professional Societies for Pharmacology
If you are interested in learning more about the exciting field of Pharmacology, I suggest that you visit the website of the American Society for Pharmacology and Experimental Therapeutics (ASPET). You can then click on the Education & Careers link near the top of the page. In the right hand column, there is a link titled About Pharmacology, that provides a great deal of interesting information. Speaking of ASPET, all scientific disciplines have their own professional societies with annual meetings that rotate cities every year, and where scientists congregate to show their results, and network. The two major professional societies for pharmacologists are ASPET, and the International Society for the Study of Xenobiotics (ISSX).
Thank you for taking the time to read this post, and I hope I was able to shed some light onto what Pharmacology is. If you enjoyed this post, you might also enjoy:
A special thank you is also extended to Dr. Paul Hollenberg, Chair of the Department of Pharmacology at The University of Michigan when I was a student, who graciously looked at this post and gave feedback prior my publishing it.
The Big Words LLC Newsletter
For the next phase of my writing journey, I’m starting a monthly newsletter for my writing and video content creation company, the Big Words LLC. In it, I plan to share inspirational words, pieces from this blog and my writers blog, and select videos from my four YouTube channels. Finally, I will share updates for my book project The Engineers: A Western New York Basketball Story. Your personal information and privacy will be protected. Click this link and register using the sign-up button at the bottom of the announcement. If there is some issue signing up using the link provided, you can also email me at bwllcnl@gmail.com . Best Regards.
“Going forward, by 2050 we’re going to have to double food production to feed the population – a tremendous responsibility. The biggest threat in my mind to that grand challenge is contamination to our water and our soil from various chemicals and toxins,” said Dr. Patrick Halbur. “We need people focused on that area to prevent and solve that problem, and so there are tremendous opportunities in Toxicology.
“We live in a world with infectious diseases and that’s always a big threat, but we almost always figure out ways to eradicate them or develop a new vaccine to solve those diseases. But the grand challenges I think are in Toxicology.”
Just briefly, Toxicology is the science of characterizing the effects of poisons (toxicants) on living organisms. The ToxMSDT program itself entails pairing up mentors in the field of Toxicology from both the public and private sectors with students from Iowa State and Tuskegee Universities. Mentors and mentees established contact prior to the weekend before meeting in person at the inaugural weekend. The weekend consisted of full slate of talks and workshops including:
Welcomes by Lisa Nola (ISU College of Veterinary Medicine), Patrick Halbur (Chair, Veterinary Diagnostic and Production Animal Medicine), Richard J. Martin (Chair, Interdepartmental Toxicology), and Wilson Rumbeiha (ToxMSDT Program PI);
A keynote presentation: Career Choices for Toxicologists by mentor Robert Casillas, Ph.D., Vice President, Strategic Global Health Security, MRI Global and the Hispanic Organization of Toxicologists (HOT);
A training titled Developing a Mentoring Relationship that Works by Barbara Johnson, Ph.D., Director of the Leadership and Mentoring Institute, affiliated with the American Association of the Blacks in Higher Education;
A student poster competition and;
A Bioethics Talk titled What is Done in the Dark? By Deloris Alexander, Ph.D. of Tuskegee University.
“Toxicologists are the guardians for human, animal and environmental health,” said Dr. Wilson Rumbeiha, Professor of Toxicology at Iowa State University and Coordinator of the ToxMSDT program. The goal of the ToxMSDT program is to support educational activities that complement and/or enhance the training of a diverse workforce to meet the nation’s biomedical, behavioral and clinical research needs. While Toxicology is an essential component of the nation’s biomedical research enterprise, there is a lack of under-represented minorities in the field where there coincidentally is a shortage of scientists in general – especially Doctors of Veterinary Medicine/Doctors of Philosophy (DVM/Ph.D.).
Toxicologists are in many places, and the field impacts many, many lives around the world. Toxicologists make the world a safer, healthier and more sustainable. That’s a message I want you to take as I proceed through my presentation,” said Colonel and Dr. Richard Casillas, one of the mentors in the program. Dr. Casillas’s talk described his educational and career paths which led him from the world of academic research to the military, and then to the private sector. A major theme of his talk was the career flexibility that his training in Toxicology afforded him.
The first 
“Going forward, by 2050 we’re going to have to double food production to feed the population – a tremendous responsibility. The biggest threat in my mind to that grand challenge is contamination to our water and our soil from various chemicals and toxins,” said Dr. Patrick Halbur. “We need people focused on that area to prevent and solve that problem, and so there are tremendous opportunities in 
Just briefly, Toxicology is the science of characterizing the effects of poisons (toxicants) on living organisms. The 
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