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Toxic Tuesdays

How Individual Variability Affects the Toxicity of Chemicals

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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How Individual Variability Affects the Toxicity of Chemicals

It’s clear that not everyone responds to the same chemical exposures in the same way. There are many examples of this. The most striking is the person who smoked cigarettes for 30 years and never had breathing problems or developed lung cancer.  A major factor in why this happens is “individual variability.”

People process chemicals differently depending on internal factors. There are two major sources of variability in people. The first is variability in the penetration of a chemical to the target organ, referred to as pharmacokinetics. The second factor is the response of the target organ and biological system itself, referred to as pharmacodynamics. Pharmacokinetics is relatively well understood compared to pharmacodynamics.

There are four sources of variability in people: uptake, distribution, metabolism and excretion. Uptake of chemicals through breathing, referred to as respiratory absorption, is mainly influenced by the solubility of the chemical in the blood and its interaction with the respiratory surfaces in the lungs. The solubility of a single chemical in the blood can differ significantly from one person to another. Solubility in the blood can even change in a single person depending on food intake and diet. How much uptake occurs alters the concentration of a chemical in the body which in turn alters its toxicity. Similarly, dermal absorption, or uptake through the skin, depends on the exposed site, the condition of the skin, and the humidity and temperature of the environment. Uptake through the stomach, referred to as gastrointestinal absorption, depends primarily on stomach content.

The distribution of chemicals in the body is also highly variable and depends primarily on body size and composition. Chemicals that are soluble in fat, for example, will be distributed differently in people with different amounts of fat. Distribution is also affected by the degree to which a chemical can bind to molecules, mostly proteins, in the body. The amount of a chemical bound to proteins in a target organ determines how much damage a chemical can cause. Chemicals that are not bound in the body are more easily removed. Chemical binding can be altered if there’s competition for binding sites due to the presence of other chemicals or drugs in the blood system.

Metabolism plays a central role in how the body responds to a chemical and is probably the most important source of pharmacokinetic variability in people. The body has different ways it can interact with or metabolize a chemical. This interaction helps determine the body’s response to chemicals. In some instances, a chemical can become more toxic and in other instances, it can become harmless. Metabolism mainly takes place in the liver but can also occur in the skin and lungs. Metabolism can be altered by several environmental factors. For example, the simultaneous absorption of chemicals in high doses can slow metabolism because of competition for the metabolizing enzyme in the body. Genetic factors also play an important role in metabolizing toxic chemicals. Individual variability in genes results from differences in the DNA sequence of genes (called polymorphisms). These individual differences play an important role in a person’s response to chemicals such as in the development of cancer. Metabolism can also be affected by age and sex, environment, chemical intake, physical activity, protein binding and lifestyle.

Once a chemical has been absorbed, distributed, and metabolized, it will be excreted from the body. The primary way that the body excretes toxic chemicals is through the kidneys. Some excretion may also occur through the lungs, GI track, skin and mammary glands in pregnant women. Renal excretion is influenced by factors such as kidney function, protein binding, urine pH and urine flow, which also varies in individuals. Volatile chemicals, chemicals with a tendency to evaporate, are generally excreted by the lungs. Pulmonary excretion is determined by the same factors that influence pulmonary absorption.

These many sources of variability mean that two people can be exposed to the same concentration of a chemical but absorb, distribute, metabolize and excrete it differently resulting in a different response. This is why scientists and government health officials struggle to explain what will happen to a group of people exposed to the same mixture of chemicals. A person’s response is highly complex and the scientific understanding of how different variables influence toxicity is not well developed. These gaps in our knowledge reflect the many uncertainties in how chemicals produce their toxic effects on the human body.  

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Toxic Tuesdays

Exposures to Chemical Mixtures Matter​

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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Exposures to Chemical Mixtures Matter

Considering cumulative exposures to low levels mixtures of chemicals is an enormous challenge when evaluating the toxicity of chemicals. Neither the EPA nor ATSDR have guidance on how to evaluate exposure to multiple chemicals simultaneously, or cumulatively over time. The EPA does have its Risk-based Screening Levels (RSLs) that provide some guidance on risk estimates, but these values only consider chemicals in isolation, or when exposed to one chemical at a time. This limitation has begun to be recognized as a fundamental weakness in the way research is done on the toxicity of chemicals. Testing one chemical at a time is not sufficient nor appropriate for evaluating public health risks when people are exposed to multiple chemicals at the same time, or cumulatively over time.  

This limitation was highlighted when a group of 350 cancer research scientists came together in Halifax, Nova Scotia to address the question of continuous multiple chemical exposures and the risks these exposures pose. Referred to as the Halifax Project, this effort merged two very distinct fields – environmental toxicology and the biological mechanisms of cancer – and provided the opportunity for researchers to look at the diversity of environmental factors that contribute to cancer by examining the impact that exposure to very small amounts of chemicals can have on various systems of the body.

These scientists looked at whether everyday exposures to mixtures of commonly encountered chemicals have a role to play in cancer causation. The researchers began by identifying a number of specific key pathways and mechanisms that are important in the formation of cancer. Then they identified individual (non-carcinogenic) chemicals that are commonly found in the environment that had some potential to disrupt these systems. A total of 85 environmental chemicals were identified.

The authors found that 59% of these chemicals (50/85) had low dose effects “at levels that are deemed relevant given the background levels of exposure that exist in the environment.” They found that only 15% of the chemicals reviewed (13/85) had a dose-response threshold and that the remaining 26% (22/85) could not be categorized due to a lack of dose-response information. The authors concluded that these results help “to validate the idea that chemicals can act disruptively on key cancer-related mechanisms at environmentally relevant levels of exposure.”

This is an important observation because it challenges the traditional thinking about how cancer forms in the body. It challenges the notion that all cancers share common traits (considered the “hallmarks of cancer”) that govern the transformation of normal cells to cancer cells. The authors also discuss how the results in this paper impact the process of risk assessment as even its most sophisticated model fails to address continuous exposures to mixtures of common chemicals. 

The authors concluded that “the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies.” In other words, exposure to multiple chemicals at low doses, considered individually to be “safe,” could result in various low dose effects that lead to the formation of cancer. This is a remarkable observation and conclusion. It is also an important advance in the understanding of the risks chemicals pose to society. It also highlights how surprisingly little is actually known about the combined effects of chemical mixtures whether on cancer related mechanisms and processes or on adverse effects in general.  

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Transgenerational Toxicity

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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Transgenerational Toxicity

While getting cancer, liver disease or central nervous system damage is often associated with exposure to toxic chemicals, one of the most sensitive targets of toxic chemicals is the reproductive system. This has long been recognized for over 50 years (1, 2, 3). In recent years however, research has shown that toxic chemicals can not only directly affect the reproductive system of both women and men, but that these effects can be passed on to the next generation and can even skip a generation. The impact of toxic chemicals on children with no direct exposure to these chemicals is known as a transgenerational effect.

A recent review paper reported that research on chemical toxicity, early life nutrition, smoking and radiation found evidence of harm even in offspring with no direct exposure to specific contaminants. This paper pointed to groundbreaking research at Washington State University that helped establish the principle of transgenerational toxicity by showing that the effects of toxic chemicals can extend even to the third generation of offspring. Other review papers have found a growing body of evidence from epidemiological studies that suggests that environmental exposures early in development have a role in susceptibility to disease in later life and that some of these effects seem to be passed on through subsequent generations (6, 7).

One important study that made this clear was a follow-up study on the residents of Love Canal in Niagara Falls, NY. This study, conducted by the New York State Department of Health (DOH), found that maternal exposure to chemicals from the Love Canal landfill was associated with an elevated risk of bearing a child with an adverse reproductive outcome. The researchers found that women who lived in the designated emergency zone while pregnant prior to the time of evacuation had a higher risk of having a preterm birth compared to women from other regions of the state. This effect was statistically significant.

There was also a greater than expected frequency of congenital malformations among Love Canal boys born from 1983 to 1996. These birth defects occurred in infants born to mothers who previously lived at Love Canal. The rate of these birth defects was about 50% higher than in boys born to mothers who lived in upstate NY. In addition, the ratio of male to female births was lower for children conceived at Love Canal. Lastly, women exposed as children had an increased risk of giving birth to a low weight baby.

These findings are consistent with the initial findings at Love Canal that led to the evacuation of the community in 1978 and 1980. The initial findings identified lower birth weight and increased congenital birth defects in infants, but were limited in defining the risk of adverse pregnancy outcomes because of small sample sizes.

This study is extraordinary because it looked at the reproductive outcomes of women after their exposure had stopped compared to other studies which typically evaluate health effects at the time when exposures were ongoing. In some cases, exposures to Love Canal chemicals occurred only when the women were children! These remarkable findings point out the subtle impact of exposure to toxic chemicals. They are a red flag for health concerns – especially for women of child bearing age – at other contaminated sites across the country. This study also highlights how little we really know about low level exposures to toxic chemicals.

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East Palestine, OH – Repeating the Mistakes of Love Canal

Photo credit: Pittsburgh Post-Gazette / Getty Images

By Stephen Lester.

Shortly after the horrific Norfolk Southern train derailment occurred in East Palestine, OH, I was invited to attend a town hall meeting organized by River Valley Organizing. The purpose of the meeting was to give people the opportunity to ask questions and hopefully, get some answers.

This was about 3 weeks after the rail company made the decision to spill the contents and then burn 5 tanker cars holding vinyl chloride and other toxic chemicals into a ditch alongside the railroad tracks at the site of the 38-car derailment. This intentional burn unleashed a gigantic black cloud full of particulates that enveloped the surrounding neighborhoods and farms in both Ohio and Pennsylvania (the accident was just a few miles from the state border).

It is well documented that burning chlorinated chemicals like vinyl chloride will generate dioxins. Dioxin is the name given to a group of persistent, very toxic chemicals that share similar chemical structures. The most toxic form of dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD. TCDD is more commonly recognized as the toxic contaminant found in “Agent Orange”  and at Love Canal, New York and Times Beach, Missouri. Dioxin is not deliberately manufactured. Rather, it is the unintended by-product of industrial processes that use or burn chlorine. It is also produced when chemicals like vinyl chloride are burned, such as what occurred in East Palestine.

At the town hall meeting, people talked about what it was like when the black cloud reached their property. One person who lived 15 miles away described burned ash material from the fire that settled on her property. Another who lived 3 miles away described how the black cloud completely smothered his property. People repeatedly asked: Was it safe for my kids to play in the yard? Is it safe to grow a garden? What is going to happen to my farm animals?

As I sat there listening, I was struck by how similar the questions were to what I had encountered when working at the Love Canal landfill in Niagara Falls, NY more than 40 years ago. People were raising important questions that deserve to be answered. But there were no clear answers. Just as it was at Love Canal.

It was also eerie how similar the response by the government authorities has been. Just like at Love Canal, the people of East Palestine are being told there’s no cause for alarm, that all the testing shows that no chemicals have been found at levels of “concern.” And just like Love Canal, the people in East Palestine are not buying it because they know things are not right. They are suffering from a range of respiratory and central nervous system symptoms including headaches, nose bleeds, runny noses, tearing eyes, and more.

As occurred at Love Canal, government scientists are not being honest with the people at East Palestine. If they did that, they would tell them what they know and what they don’t know. That would be helpful. But government won’t do that, because if they do, if they acknowledge how little is known about the link between adverse health effects and exposures to mixtures of chemicals, the people of East Palestine would demand action in the face of the huge uncertainties. Actions like paying for people to relocate from the area so that they can stop being exposed to the toxic chemicals – which are still in the air – or getting the health care they need and moving on with their lives.

It’s also unfortunate that so little had changed in the science of what we know about what happens to people who have been exposed to mixtures of chemicals like what occurred in East Palestine. This might have been understandable 40 or so years ago, but not today. It’s inexcusable that we didn’t learn from Love Canal and are repeating the same mistakes because we still know very little about widespread exposures to chemical mixtures.

The people in East Palestine deserve to be treated with respect and dignity and that includes expecting their government to act to protect their health in the face of the many uncertainties that exist in understanding the adverse health effects that result from these exposures. It’s time to do right by the people of East Palestine.    

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Toxic Tuesdays

Epigenetic Toxicity

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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Epigenetic Toxicity

The way scientists think about how chemicals cause their toxic effects is changing. Recent scientific research tells us that the traditional notion of how chemicals act is being replaced by a better understanding of the actual features of exposures that influence how chemicals express their adverse effects in people. These features include the timing and vulnerability of exposures, exposures to mixtures, effects at low doses and genetic alterations called epigenetics.

It wasn’t too long ago that scientists believed that the DNA in our cells was set for life, that our genes would be passed on from one generation to the next, and that it would take generations to change our genetic makeup. This is no longer the case.

A new research area, called epigenetics, is perhaps the fastest growing field in toxicology and it is changing the way we think about chemical exposures and the risks they pose. Epigenetics is the study of changes in DNA expression (the process of converting the instructions in DNA into a final product, such as blue eyes or brown hair) that are independent of the DNA sequence itself.

Researchers are learning is that the “packaging” of the DNA is just as important as a person’s genetic make-up in determining a person’s observable traits, such as eye color, or their susceptibility to diseases such as adult on-set diabetes or lupus.

We are learning that the environment is a critical factor in the control of these packaging processes. We may be born with our genes, but epigenetic changes can occur because of environmental influences and exposures during development and throughout life. These influences include reactions to the chemicals in the food we eat, the air we breathe, the water we drink, and they appear to contribute to the development of cancer and other diseases.

Researchers have found that the genome, which is a person’s complete set of DNA, responds to toxic chemicals in the environment that a person is exposed to. It can lead to changes in gene expression, not by mutating the genes, but by sending subtle signals that stops gene activity or turns them on at the wrong times. Researchers believe that the genome has evolved from adapting to stressful survival situations to becoming more vulnerable to adverse environmental exposures, which leads to direct changes in people’s health based on how they respond to toxic chemicals in their environment. Linda Birnbaum, the former director of the National Institute of Environmental Health Sciences and the National Toxicology Program, put it this way: exposure to gene-altering substances, particularly in the womb and shortly after birth, “can lead to increased susceptibility to disease. The susceptibility persists long after the exposure is gone, even decades later. Glands, organs, systems can be permanently altered.”

This growing field of epigenetic toxicity may explain the long-term effects of chemical substances and the predisposition to disease that some people have due to environmental factors including exposure to chemicals. Epigenetics may also help to explain why certain people develop diseases and others do not, or why the person who smoked for 30 years never developed lung cancer.

There is still much to learn, but an early lesson to take away from this emerging science is that we need to rethink our traditional ideas of how chemicals affect our health. This is especially true since regulators and public health scientists who make decisions about safe levels of exposure to toxic chemicals are not considering epigenetic toxicity in their evaluations and are missing a critically important piece of the toxic chemical exposure puzzle. This may help explain why government is constantly telling people that the testing that has been done shows no cause for concern, while the people who have been exposed have symptoms and illnesses with no explanation for why they are sick.  

For more information on epigenetic toxicity, see these resources:

1. https://www.healthandenvironment.org/environmental-health/social-context/gene-environment-interactions

2. https://www.sciencedirect.com/science/article/pii/S0278691517305240

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CTEH: The Fox in the Chicken Coop

Photo credit: Rebecca Kiger, The Washington Post/Getty Images

By Hunter Marion.

On March 12, 2023, ProPublica published an article in which CHEJ’s Science Director, toxicologist Stephen Lester, was commented as saying that “[Norfolk Southern] is responsible for the costs of cleaning up this accident.” The article went on to inform how the company was going about backing the bill for this cleanup.

Norfolk Southern has recruited the private environmental firm, Center for Toxicological and Environmental Health (CTEH), for the monitoring and removal of residual vinyl chloride and other chemicals. The problem with this choice is that CTEH has been the go-to company for alleged big polluters to utilize and sign-off on their controversial cleanups.

So, what is CTEH? It is an Arkansas-based company that, according to its website, is “committed to safeguarding your workers, your community, and the environment.” However, their record shows that this messaging is directed more towards compromised companies rather than harmed citizens. Starting in 1996, CTEH gradually gained prominence amongst alleged big polluters for performing toxicological evaluations and risk assessments that environmentalists would argue as being pro-industry.

  • In 2006, CTEH seemingly downplayed the health impacts of hydrogen sulfide in a report they wrote for the Chinese construction company, Knauf Plasterboard Tianjin, about their drywall. This drywall was later discovered to be highly toxic in 2009 and led to two giant class-action lawsuits in the U.S.
  • In 2008, 5.4 million cubic yards of coal ash broke through a 57-foot dike maintained by the Tennessee Valley Authority and flooded the town of Kingston, TN. While assessing the largest industrial spill in U.S. history, CTEH allegedly failed to meet quality assurance standards and used inaccurate air monitoring procedures during an audit. Arguably, the results of these actions disguised the true extent of the airborne coal ash that was present.
  • In 2010, CTEH purportedly underwent covert operations to release Corexit (a highly toxic dispersant) upon millions of gallons of crude oil during the Deepwater Horizon ocean spill. This resulted in the appearance of oil removal, until the following winter when it was shown that the oil was pushed further underwater and diverted to nearby watersheds and protected wetlands.
  • In 2016, a Husky Energy pipeline burst and poisoned a river with roughly 250,000 liters of crude oil within the James Smith Cree Nation in Saskatchewan, Canada. CTEH supposedly created a testing zone excluding the waterways most affecting the First Nations community. The results came back inconclusive, which likely justified Husky Energy to continue ignoring the community’s cries of concern.
  • In 2019, the International Terminals Company’s chemical storage facility in Houston, TX caught on fire. The resulting smoke cloud that covered most of the city released 9 million pounds of pollutants in one day, shutdown many municipal school districts with shelter-at-place advisories, and exposed the nearby city of Deer Park to extreme amounts of benzene (citizens later suffered severe symptoms). Afterwards, CTEH apparently performed insufficient air quality tests. Their dubious results were readily approved by the Texas Commission on Environmental Quality (TCEQ) and EPA.

Numerous toxicologists and environmental experts have decried CTEH’s methods as being suspicious to sinister. Activists and even politicians have warned against using their services (most notably during the Deepwater Horizon fiasco). Now, CTEH has been given the authority to control the narrative about how many toxic chemicals are truly present in East Palestine. As observed by former Exxon chemical engineer, Nicholas Cheremisinoff, CTEH is “essentially the fox guarding the chicken coop.”

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Why Are We Unprepared for Environmental Disasters?

Photo credit: Matthew Hatcher/Bloomberg via Getty Images

By Leila Waid.

The train derailment in East Palestine, Ohio, shows that our country is unprepared to address environmental emergencies adequately. Environmental disasters of the past show that accidents, just like human error, are inevitable. But how our society responds to these events can make all the difference. It can mean the difference between a life lost, and a life saved.

The Norfolk and Southern train derailment carrying toxic materials, such as ethanol and propane,  was not the first environmental emergency facing our country. Other human-made ecological disasters that have impacted the health and safety of the communities include the Love Canal toxic waste site, the Exxon Valdez oil spill, the Deepwater oil spill, the California fires caused by the Pacific Gas and Electric Company, and the Ringwood Mines Landfill Site.

There is no certainty that such destructive environmental events, like East Palestine, will never happen again, especially since there are an average of three train derailments per day. Of note, the Norfolk and Southern CEO, Alan Shaw, refused to support the Railway Safety Act of 2023 during the March 9, 2023 Senate hearing on the derailment. Shaw’s lack of commitment to safety improvements is even more staggering in the context of another one of the company’s trains derailing the morning of the hearing. During the hearing, Shaw also refused to commit to covering the healthcare costs of the community members impacted by the toxic fumes released into the air.

So, if it is likely that these events will keep happening and communities will keep facing environmental injustice. What can be done? One solution is to create a national response team within the Environmental Protection Agency (EPA), called the EPA National Response Center (EPANRC). Within this proposed EPANRC, a Rapid Response Team would be created that is tasked with monitoring potential environmental hazard scenarios and be equipped to respond quickly to various toxin-related emergencies. The proposed EPA Rapid Response Team (EPARRT) would consist of multiple experts with different skills, including toxicologists, epidemiologists, environmental health scientists, public health emergency planning officials, and communication experts.

A model like the one proposed already exists for other federal agencies. For example, the Food and Drug Administration (FDA) have protocols in place for when contaminations are found in the food supply, such as when E.coli was detected in lettuce. The Centers for Disease Control and Prevention (CDC) also have various resources and teams in place to address infectious disease outbreaks. With the increasing number of actual train derailments and potential derailments, now is the time that environmental justice emergency issues are provided equal attention and the same amount of support at the national level, like the ones which already exist at the CDC and FDA.

How would an EPA National Response Center benefit the impacted communities? The guiding principle of the Center would be to protect the communities and empower them with timely and vital information. For example, if such a Center existed for East Palestine, it could have prevented the controlled burn of hazardous material in five train cars. In the Senate hearing, Eric Brewer, the fire chief who was one of the first responders on the scene of the accident, thought the decision to go from burning only one of the train cars to five as shocking and astounding. Scientists argue that the act of burning off the material in those trains released dangerous toxins into the air. Specifically, it could have caused the community to be exposed to dioxin, one of the most harmful toxins to human health.

One of the main themes expressed by the East Palestine residents is frustration with the lack of answers given to them by Norfolk and Southern, state, local and federal governments. The proposed EPA National Response Center (EPANRC) would have a framework for interacting with the community immediately and providing them with the most transparent information on a minute-to-minute basis. The EPANRC would not work in a bubble but instead organize and collaborate with the community leaders directly and immediately to provide them with necessary resources and information.

Another benefit of having the proposed EPANRC would be to address community issues directly and would not rely on the politics of the local, state or federal governments. Also, what is often overlooked, is that environmental disasters do not stay within the state or regional borders. The impact of these types of disasters affects communities that are miles away from the initial impacted community. For example, the train derailment in East Palestine happened right next to the Pennsylvania border. Now residents in Pennsylvania are just as harmed by the toxins, as those in East Palestine, Ohio.

Like the event in East Palestine, when an environmental disaster happens in a small town that does not have the resources to respond to it, that should not mean that the people in that location must suffer the consequences of having toxic air and water in their communities. This proposed EPANRC would make sure that all environmental disasters are handled with the safety of the people as the priority and would safeguard and allocate the resources to make that happen.

The bottom line: No matter where someone lives or what their zip code is everyone deserves access to a clean and safe non-toxic environment.

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Toxic Tuesdays

From Risk Assessment to Presumption

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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From Risk Assessment to Presumption

The last several issues of this series in Toxic Tuesday have addressed the difficulty in interpreting health risks when people are exposed to toxic chemicals. The last issue focused on the failure of the risk assessment approach to address these difficulties and the many critical limitations which make it inadequate and inappropriate for assessing public health risks. 

Despite these limitations, the government still relies on the risk assessment model as the “go-to” method to determine if the health problems people are suffering are due to exposures occurring or suspected of occurring in a community. Risk assessment fails to answer the basic question that people ask when exposed to toxic chemicals: How will my health, or the health of my children or family, be affected by these chemicals?

What we have seen over the years is that risk assessment cannot answer this question, no matter how well done or how much context is provided to help reduce misuse and misunderstanding. People exposed to toxic chemicals live for years with their exposures as scientists do health studies, health assessments, evaluate data on exposures and try to estimate risks. In most cases, people are told that the risk assessment shows that the level of toxic chemicals that people were exposed to are not likely (or some similar caveat) to cause any adverse health effects. Consequently, little, if any action is taken to protect communities exposed to toxic chemicals.

As part of CHEJ’s Unequal Response Unequal Protection campaign, we have been working with community leaders and environmental health scientists to develop a new approach that centers community leadership to address the difficult questions about chemical exposures. Instead of trying to determine if the health problems reported in a community were directly caused by the specific exposures to toxic chemicals occurring in that community, we adopted the approach  used by the federal government when considering adverse health effects suffered by veterans, active military, first responders, 9/11 victims and others exposed to toxic chemicals while serving their country.

In these situations, the government recognized that critical scientific information linking exposures and health outcomes was missing or incomplete thus making it necessary to make “presumptions” about exposures leading to the health problems suffered by these groups. This recognition led to the government providing health care, treatment, compensation and other assistance needed due to exposure to toxic substances suffered while serving our country. In communities where people have been exposed to toxic chemicals through no fault of their own, the government would extend a similar application of the presumptive approach. 

The presumptive approach asks what scientific information is sufficient to take action to protect people exposed to toxic chemicals? We propose the following approach to answer this question.

  1. Using existing and newly generated environmental sampling results collected in the impacted area, government (or an expert team of scientists) would compile a list of toxic substances to which the community is exposed.
  1. An independent committee of environmental and public health experts would then review the literature and determine what adverse health effects/diseases are associated with the toxic chemical(s) identified. Exposure to a chemical will be presumed to cause an adverse health effect if the evidence linking the chemical and the health effect is at least as likely as not, based on the strength of the studies found. The diseases with a positive association to the toxic substances present in the community would be used to decide which diseases will be presumed to be associated with the chemicals identified in the community.

Based on results of this approach, appropriate action to safeguard the health of the community can be taken. This decision could include remedies to lessen exposures and lessen the risk of injury and the effects of exposure. They might also include evacuation, providing a clean water supply, closing a polluting facility or implementing new emissions limitations.

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Classic Toxicology No Longer Works

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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Classic Toxicology No Longer Works

The dose makes the poison is the most basic principle of toxicology. The first chapter in every toxicology textbook discusses how the response to a poison depends on how much of the poison you are exposed to (often referred to as the “dose”). This principle assumes that chemicals act by overwhelming the body’s defenses at higher doses. It also assumes that at some lower dose, there is no harm or no effect.

But this basic principle may no longer hold true as what we know about exposures to toxic chemicals is changing. Some time ago, Linda Birnbaum, former director of the National Institute for Environmental Health Sciences, wrote an overview paper on the changing science in the field of environmental health. She wrote in this paper that the antiquated perception of how chemicals act is being replaced by a “better understanding of the actual characteristics of modern environmental chemicals.”

These characteristics include the timing and vulnerability of exposure, exposures to mixtures, effects at low doses, and genetic alterations called “epigenetics.” Birnbaum addressed each of these frontiers of toxicology and discussed how each affects our understanding of the link between the environment and public health.  

It’s clear now that the body’s response to toxic chemicals is complex and not as predictable as classic toxicology would lead us to believe. Chemicals such as bisphenol A (BPA) and dioxin cause adverse effects at low doses, not predictable by classic toxicology. No longer can you safely assume that at some low dose there is no harm. Birnbaum makes it clear that within traditional toxicity “… [testing] of effects at some high doses are no longer adequate to [determining] the full spectrum of response from a given chemical.” What’s more, the effects observed at low doses may be different than those observed at higher doses.

We also now know that there are critical “windows of exposure” during development that determine effects – the same exposure at different times can result in different effects. There are also enhanced periods of vulnerability during prenatal development that “program” the bodies’ physiology leading to diseases in later life. According to Birnbaum, this phenomenon has been demonstrated for hypertension, coronary heart disease, and neurological and cognitive development.

Another advance in our understanding of toxicology comes from the field of epigenetics, or the study of changes in DNA expression that are independent of the DNA sequence itself. We now know that exposures to chemicals can alter the normal triggering mechanism that turns genes on or off that determines a person’s observable traits, such as blue eyes or susceptibility to diabetes or other illnesses. Says Birnbaum, “[We’re] born with our genes, but epigenetic changes occur because of environmental influences during development and throughout life.”

These advances in toxicology raise many questions about the adequacy of traditional methods of assessing the impact of exposure to chemicals like BPA or dioxin, not to mention mixtures. Regulatory agencies have not integrated this new science into the methods they use to assess public health risks and it’s likely to take some time before traditional toxicologists accept this new thinking and integrate it into their methods for assessing public health risks. In the meantime, recognize that some of what public health officials are telling you is antiquated and no longer applicable to the world we live in.

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The Role of Science and Information in Addressing Questions about Chemical Exposures

Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

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The Role of Science and Information in Addressing Questions about Chemical Exposures

It’s common to think that in science and technical information lies the answer to the many questions people ask about exposures to toxic chemicals. At CHEJ, we have not found this to be the case. While science and technical information is very important, by itself it cannot answer most of the questions people raise about exposure to toxic chemicals. People want answers and they want action to address the contamination in their community. Science and technical information can play a vital role in helping to achieve community goals, but identifying this role and learning how to use scientific and technical information is critical to the success of a local group. 

Many assume that if you hire the best scientists and engineers and make solid technical arguments, the government will do the right thing. It rarely works that way. It’s not because people who work for government don’t care, it’s just that the science is not there for government to justify acting. This is primarily because of the lack of scientific knowledge and understanding of how exposures to toxic chemicals lead to health outcomes in people. Scientists know little about the adverse health effects resulting from exposure to combinations of chemicals at low levels. As a result, when politicians and bureaucrats look for answers, the scientists usually don’t have them. 

At first glance, this may not make sense. We know so much about many toxic chemicals, like lead and dioxins, for example. But when it comes right down to it, we know very little about what happens to people when they are exposed to low level mixtures of toxic chemicals, even those that include lead and dioxins.

We can estimate risks and talk about the hazards associated with exposure, but we just don’t know much about the mechanisms of how chemicals damage the human body, especially in low level mixtures over long periods of time. This is because in most cases, there is very little information about what a person is exposed to, the concentration they are exposed to, and for how long. A person’s health conditions and prior exposures to toxic chemicals also play a role. In addition, there is no way to distinguish or fingerprint an exposure with a health outcome. 

Most scientists are reluctant to discuss how little is known about the link between health outcomes and exposures. Instead, the tendency is to discuss the “risks” of exposure which eventually leads to a debate over what’s an “acceptable” risk. This process hides the fact that scientists don’t know what happens to people who are exposed to low levels of a mixture of toxic chemicals. 

Because of this lack of scientific clarity, bureaucrats and politicians use “science” cloaked in uncertainty, not facts, to justify decisions which are based on the political and economic pressures they face. It is naïve to think that science and the many uncertainties resulting from exposures to toxic chemicals can serve as anything but a tool used by politicians and corporations to do what they want. 

In the face of these uncertainties, government sees as its main role and primary responsibility to maintain control of a situation and to assure the public that everything is fine, whether it is or not. The government cannot afford to say what it really knows about a situation, which often, is very little. If they did that, then the public would demand action that they could not scientifically justify taking. 

Despite these realities, there is a critically important role for science and information to play in addressing exposures to toxic chemicals. This role is to document the exposures and risks posed by these exposures and to support the arguments of activists and people exposed to toxic chemicals. The role of science and technical information is to be part of a larger strategic plan to help the community and the individuals who have been exposed to toxic chemicals achieve their goal, whether it’s to be relocated, or to achieve cleanup of a contaminated site. It’s important to recognize what science and technical information can tell you and what it can’t. 

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