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One Year Anniversary of the Train Derailment in East Palestine, OH

Photo credit: Abigail Bottar / Ideastream Public Media

By Leila Waid.

It’s hard to believe that it has already been one year since the Norfolk Southern train derailed in the small and quiet community of East Palestine, OH. The community members have faced uncertainty and fear of how their health has been impacted by the exposure to toxins, such as vinyl chloride, present at the burn site. Burning vinyl chloride can produce dioxins, a chemical that poses immense danger to human health. Over the year, many residents have spoken out about the health risks they are experiencing, such as increased asthma in their children, skin rashes, bleeding from the ears, and new diagnoses of cancer. Also, residents have pointed out how the train derailment has impacted them financially. One of the residents, Ashley McCollum, talked with ABC News about how she has been displaced from her home for the past year. Unfortunately, Norfolk Southern, who had been paying for her and her family to stay in a hotel, said they would no longer fund her accommodations. Now Ashley and other displaced residents have a hard choice to make – return to the community they believe will make them sick or come up with alternative living arrangements with their own finances.


This harsh abandonment that many residents have experienced feels all the more infuriating when considering how much Norfolk Southern has spent on lobbying. According to Public Citizen, “the company and its subsidiaries spent $2,340,000 lobbying the federal government in 2023 – up 30% from the $1,800,000 it spent the year before.” Interestingly, no new railroad safety legislation was passed by Congress after the Norfolk Southern train derailed. One would imagine that when such a severe accident occurs that threatens the health of thousands of people, the policymakers would immediately work in a bipartisan manner to make sure that such an accident never happens again. Notedly, both the House and the Senate introduced bills to increase railroad safety, but a year later, those bills have not moved forward. House of Representatives member Marcy Kaptur directly connects the lack of action by Congress on the bills to the lobbying being carried out by railroad companies, such as Norfolk Southern.


Without stricter regulation, who knows when and where the next derailment might occur and which American town could be the next East Palestine.

Frustrated by the lack of answers and support, the impacted community in East Palestine created the Unity Council for the East Palestine Train Derailment. One of the most recent actions the Council undertook was a “ceremony of solidarity,” an event held on the first anniversary of the train derailment to raise awareness about the suffering the community is still going through. The Council wanted to showcase to the country that what happened in their community could happen anywhere in the country.


The ceremony was conducted in partnership with We Refuse to Die, an environmental justice campaign utilizing art to communicate the message. Artists and activists have a long history of working together effectively to enact change. By moving people emotionally, artists can tap into the feelings and emotions of individuals that motivate them toward change. In this case, the campaign was focused on showcasing that, just because individuals in East Palestine may have been forgotten about by the railroad industry and politicians, they are still here and will continue to fight until they can rebuild what was stolen from them by the explosion.

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Planetary Health and Environmental Justice

Photo source: https://www.sciencedirect.com/science/article/pii/S2542519621001108

By Leila Waid.

Planetary health is a term used to define how human activity impacts the environment and, in turn, how those environmental changes impact human health. Utilizing a planetary health framework is essential for environmental health organizing because it uses a holistic approach to understanding the world and our place within it. The Planetary Health approach showcases that protecting our environment is not something we should do because it is simply the right thing, but we need to do it for our preservation and well-being. 

The air we breathe is littered with pollution from fossil-fuel industries. Even antibiotic resistance, a major emerging public health threat, has connections to air pollution. For example, a study found that PM2.5 (particulates in the air smaller than a strand of hair) contain antibiotic-resistant bacteria. Shockingly, the study found that “the magnitude of the contribution of PM2.5 to aggregate antibiotic resistance is greater than that of antibiotic use.”

Our waterways are full of plastics and PFAS, a group of forever chemicals that bioaccumulate in the body. The fish we consume are saturated with methylmercury due to humanmade activity, such as coal mining that dumps excess mercury into the waterways. And we keep pumping greenhouse gases into the environment, which causes warming and a disbalance in our delicate climate system. Interestingly, even the knowledge that we are driving the deterioration of the natural world causes stress and other mental health issues – a phenomenon coined “eco-anxiety.” On the other hand, being in nature does wonders for our mental health, such as decreasing anxiety and depression. 

So, what can be done? How can we keep our quality of life, with all our modern conveniences, while understanding that profound changes must be made to preserve the ecological world and our health? Two public health experts, Tong and Bambrick, weigh in on this issue in a peer-reviewed article, in which they provide four suggestions.

According to Tong and Bambrick, we first need to address the root cause of climate change globally and utilize different approaches based on regional and national contexts. Second, we must address environmental justice at all levels, from international to hyper-local. Third, we must understand that the entire world is interconnected, and we live in a “global village.” Our air and waterways do not have national boundaries, and the air pollution on one side of the world can eventually reach your backyard. Nowhere was this more apparent than the summer of 2023 on the east coast of the U.S. when the Canadian wildfire plume traveled south and made the air unbearably smoggy. The fourth, and final, suggestion states that we must take collective action at an international level. After all, these are not issues that one individual or country can tackle. Instead, we need to reimagine our way of life that is focused on being connected to our environment, respecting our limited natural resources, and protecting human health.

Planetary health lays out the vicious cycle that modern humans face. We have built our way of life not in tandem with the natural world but in its exclusion. And as a result, we face the health consequences of those choices. 

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It’s Time to Do Right by the People in East Palestine, OH – and Elsewhere

Photo credit: CNN

By Stephen Lester.

Nearly 10 months ago, a Norfolk Southern train with more than 150 cars, many of which contained toxic chemicals, derailed in East Palestine, OH. Thirty-eight of the train cars derailed and a decision was made by Norfolk Southern to burn the contents of 5 tanker cars containing vinyl chloride and other toxic chemicals. This unleashed a huge black cloud full of particulates that enveloped the surrounding neighborhoods and farms in both OH and PA.

Immediately after the burn, people in East Palestine began reporting adverse health symptoms including headaches, nose bleeds, skin rashes, central nervous symptoms, thyroid problems and more. These and other adverse health problems have continued to plague the residents of this rural midwestern town.

EPA immediately responded by telling people that everything was alright and there was no cause for alarm. EPA’s testing found no levels of “concern.” But the people in East Palestine could not accept this narrative because they knew things were not right. They knew the health effects they were suffering from were real. They knew that EPA was not telling them the truth.

If EPA were honest with the people at East Palestine, they would have told them that they didn’t understand why people were continuing to report so many illnesses while their data told them otherwise. But if EPA did 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 these uncertainties. Actions like paying for relocations so that they can stop being exposed to the toxic chemicals that are still in the air and getting the health care they need to move on with their lives.

The people in East Palestine deserve better. So do hundreds of other communities across this country where people have similarly been exposed to low levels mixtures of toxic chemicals. It is clear from the situation in East Palestine that very little is known about how people respond to chemical exposures, especially to low level mixtures. This is evident when the EPA and other public health agencies who rely on traditional toxicology and risk assessment are telling the people of East Palestine that everything is safe when it clearly is not.

It’s time to acknowledge that the scientific understanding does not exist to explain what is happening to the health of the people in East Palestine. It’s time to recognize that we cannot rely on traditional toxicology to answer the questions people have about their exposures to low level chemical mixtures. It’s time to do the right thing by the people in East Palestine and by hundreds of communities across the U.S. where people are being exposed to low level mixtures of toxic chemicals. It’s time to acknowledge that the tools we have are not able to answer the questions people raise about their exposure to toxic chemicals and give people the relief they are asking for, whether it’s cleanup, relocation, health care or something else.   

It’s what the government did for the Vietnam veterans exposed to Agent Orange; for the atomic bomb victims exposed to radiation fallout; for the 9/11 first responders in New York City; for the soldiers exposed to burn-pit smoke in Iran and Afghanistan and other overseas locations; and for the Marines at Camp Lejeune, North Carolina who drank contaminated water. Do the people of East Palestine deserve anything less than the soldiers and first responders who protect this country?

In each of these instances, the government recognized that the science linking exposure and health outcomes was incomplete and instead of requiring proof of cause and effect, they said, “Enough, we will take care of our own.” They moved to a presumptive scientific approach that allowed veterans and first responders to  health care and other compensation. We should do the same for the people of East Palestine and in hundreds of other communities that have been exposed to low level mixtures of toxic chemicals.

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Toxic Tuesdays

How Individual Sensitivity Affects Toxicity

Toxic Tuesdays

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

How Individual Sensitivity Affects Toxicity

We previously addressed individual variability and how it affects a person’s response to toxic chemicals. Another important factor in toxicology is a person’s individual sensitivity to chemicals. How sensitive a person is to chemical exposure helps determine how susceptible or vulnerable they are to toxic chemicals. Several factors determine how sensitive a person is including age, sex, health, genetics, diet, lifestyle, preexisting conditions and previous environmental exposures. While some people are more sensitive to chemical exposures than others, there is no clear definition of what sensitivity is or what it means. This is partially since so little is understood about the human response to toxic chemicals, especially to low level mixtures of chemicals.

Because of this uncertainty, there is no generally accepted definition of sensitivity. Nicholas Ashford and Claudia Miller describe the various meanings of the term. In traditional toxicology, sensitivity has been defined as individuals who require relatively lower doses to induce a particular response. These individuals are considered more sensitive than people who require relatively higher doses to experience the same response. The distribution of this population is described by the classic bell curve where the sensitive and resilient populations are found in the tails of the curve. Most people fall into this response category. In traditional medicine, sensitivity has been defined as individuals who have a significant and rapid immune-mediated response to an allergen or agent. In this population, some individuals, described as chemically sensitive, have a striking immune response to an allergen or agent, while non-allergic individuals do not, even at high doses. Classic allergens include ragweed or bee venom, but also include chemicals such as nickel or toluene diisocyanate (TDI).

In recent years, a growing population of people have expressed an entirely different sensitivity response. These are people who have developed multiple chemical sensitivities. Ashford and Miller found that people who have developed multiple chemical sensitivities may exhibit a third and entirely different type of sensitivity. These authors stated this about people with multiple chemical sensitivities (MCS): “Their health problems often (but not always) appear to originate with some acute or traumatic exposure, after which the triggering of symptoms and observed sensitivities occur at very low levels of chemical exposure. The inducing chemical or substances may or may not be the same as the substances that thereafter provoke or ‘trigger’ responses.” Unlike classical toxicological or immune mediated responses, people with MCS sensitivity respond in a two-step process of an initial exposure event followed by a second triggering exposure. Much still needs to be understood about this third wave of sensitivity.  

Another factor that influences a person’s sensitivity is the body’s reserve capacity. Researchers have speculated that a chemical exposure may affect the reserve capacity of the body without causing an immediate adverse effect. However, when there are subsequent exposures, the body becomes unable to compensate for the additional stress and toxicity develops.

The science behind what is known about how people respond to chemical exposures, especially to low level mixtures of chemicals, is highly complex and not well understood. We know that people exposed to low level mixtures of toxic chemicals, like the people in East Palestine, OH, the site of that horrific train derailment and subsequent intentional burn of vinyl chloride, continue to suffer adverse health effects despite reassurances from EPA and public health agencies who are relying on traditional toxicology and risk assessments. Perhaps the people in East Palestine have developed a unique chemical sensitivity much like the third wave described by Ashford and Miller. So as their exposures continue during the ongoing cleanup, their chemical sensitivity and the subsequent adverse health responses are not what would be predicted by traditional toxicology or medical models. 

This is an important consideration to consider in East Palestine because it is clear that we do not understand what is happening to the health of the people there. It’s time to recognize that we cannot rely solely on traditional toxicology to address the questions people have about exposures to low level chemical mixtures.

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Cyanide

Cyanide is a chemical usually found in compounds with other chemicals. Cyanide compounds can be

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How AI Can Help Strengthen Grassroots Organizing

Image Credit: Tensorspark

By Gregory Kolen II.

Environmental justice is an issue that affects everyone, but those who bear the brunt of it are often the most vulnerable members of society. Disadvantaged communities, specifically, are often the ones living in areas with poor air quality, contaminated water sources, and unregulated disposal of waste. These challenges have been longstanding and difficult to overcome, as they require significant resources and political will. Yet, in recent years, emerging technologies such as Artificial Intelligence (AI) have emerged to support community leaders and organizations working towards environmental justice.

Boosting activism through data: AI can assess and analyze vast amounts of data to help grassroots organizers tailor their messaging based on the demographics, behavior, and attitudes of their target audience. By better understanding the needs of the communities they serve, organizers can create more effective and convincing campaigns that are more likely to drive action.

Streamlining operations: Organizers can improve the efficiency of their operations and decision-making processes, allowing them to work more effectively and achieve their goals more quickly. AI can help organizers automate routine tasks, which saves time and energy, allowing them to focus on more complicated tasks that require human expertise.

Amplifying voices: Magnify the voices of marginalized communities with AI-powered chatbots. Amplify the stories and experiences of those most affected by environmental injustices. This can help grassroots organizers build empathy and support for their causes among those in power, as well as among the broader public.

Improving outreach: Organizers can reach out to a more extensive and precisley targeted diverse audience. AI-powered tools can help create more targeted promotional materials and reach out to individuals who might not have been reached through traditional methods. This can help organizers increase the reach of their initiatives and attract more support.

Identifying environmental issues in communities: AI tools can help communities identify and monitor environmental hazards in their surroundings. For instance, using machine learning and remote sensing technologies, it is possible to map and classify toxic hotspots or areas with high pollution levels. Real-time air and water quality monitoring sensors can also provide early warning systems that allow communities to take the necessary precautions.

Empower communities through data and citizen science: Citizen science is an approach that empowers communities to gather data, conduct research, and create solutions. AI tools can help democratize scientific research by enabling communities to communicate their findings and analyses. Collectively, high-quality data can be used to ascertain environmental health disparities. For instance, EarthAI, a nonprofit organization, aims to provide equal access to AI-assisted satellite imagery, which can be used to map and track environmental health indicators.

Influencing Policies: AI tools can be used to predict the impact of policies on marginalized communities. For instance, researchers can use machine learning models to identify areas where environmental policy interventions are most needed, based on critical community characteristics and environmental hazards. Such data and insights can be shared with policymakers to develop effective policies that prioritize environmental justice.

There are numerous ways that emerging AI technology can be used to help strengthen grassroots organizing efforts for environmental justice. From boosting activism through data analysis to amplifying voices and improving outreach, AI has the potential to help empower grassroots organizers and create more profound change by identifying environmental hazards, empowering communities through data and citizen science, influencing policies, raising advocacy and awareness, and reducing disparities. While AI is not a magic solution, it has the potential to create a pathway towards a more just future and better outcomes for all communities.

Additional information:

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Health Effects of PFAS in Drinking Water

The glass is always... we're screwed comic.
Image credit: Jim Morissey

By Leila Waid.

As a research project for a university course, I conducted a literature review and systematic analysis of the health effects of PFAS in drinking water. This blog post contains a highlight and broad overview of the health effects discovered.

The systematic analysis included 44 observational epidemiological studies focused on PFAS-contaminated water as the exposure and adverse health effects as the outcome of interest. (For inquiries, references to individual studies, or any other information about the information about the systematic review study, email info@chej.org).

The results:

PFAS in drinking water is associated with a variety of different health effects. However, it is important to note that the results included here do not prove causation. In other words, the studies cannot prove that PFAS caused these health issues, only that an increase in PFAS exposure is associated with these health effects.

  • Cardiovascular health: increase in “bad” cholesterol, triglyceride lipids, blood pressure, hypertensive pregnancy disorder.
  • Hormonal health (endocrine system): impaired thyroid function, disruption in the growth hormone IGF-1 in children, lower levels of estradiol and testosterone, increase in Poly-Cystic Ovary Syndrome, fibroids, and testicular cancer.
  • Immune health: increase in adverse health effects from COVID-19, disruption in inflammation production, lower immune cell count and production, increase in ulcerative colitis (stomach ulcers).
  • Urinary system health: kidney function impairment, kidney cancer, bladder cancer
  • Digestive system: esophageal cancer.
  • Neonatal (infant) health: lower birthweight and small for gestational age.
  • PFAS has also been found to cause epigenetic changes, which is a process through which our environment impacts how our genes are expressed. In other words, it does not change the actual DNA structure, but how the body reads the DNA sequence. Specifically, PFAS is associated with DNA methylation (a process through which chemicals attach to a DNA chain and turn a specific gene on or off. This process affects how the gene is read).
  • Mortality: exposure to PFAS associated with all-cause mortality, as well as mortalities from liver cancer, cerebrovascular disease, diabetes, myocardial infarction, kidney cancer, breast cancer, and Alzheimer’s disease.
  • Neurological system: developmental language disorder.
  • Skeletal system: increase in bone fractures (hip, proximal humeral, and distal forearm fractures).
  • Non-regional specific: mesothelioma cancer (affects tissues around organs), increase in multi-morbidity (multiple chronic morbidities occurring at the same time).
  • Mental health: increased anxiety, financial stress around health issues, emotional distress due to worrying about living in PFAS-contaminated region. Also, PFAS was associated with an increase in behavioral problems among children. 

It is important to note that all the adverse health effects discussed above were found from observational studies on human health, not animal or in vitro (cell) studies. Although the findings cannot prove causation, they still paint an alarming picture for human health. The results showcase that urgent and robust policy action is needed at the federal and state levels to protect our waterways from PFAS contamination. This situation is critical because almost half (45%) of all tap water systems in the U.S. have PFAS contamination. And one study found that an estimated 97% of all Americans have PFAS in their blood streams.

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Toxic Tuesdays

Metals & Preterm Births

Toxic Tuesdays

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

Metals & Preterm Births

Over 10% of births worldwide are preterm, meaning delivery occurs earlier than 37 weeks of pregnancy. It is a leading cause of neonatal mortality, and evidence suggests that exposure to heavy metals from the environment could be a risk factor. In the US, a major source of exposure to metals is private well water. The Environmental Protection Agency (EPA) sets standards and regulates levels of contaminants in public drinking water, but private well water isn’t regulated. This means private well water – which 13% of the US population receives drinking water from – is vulnerable to contamination. Indeed, studies have found metal contamination in private wells and that people who receive drinking water from private wells have more of these metals in their systems.

A recently published study set out to evaluate if exposure to toxic metals from private well water increased the risk of preterm birth. Because North Carolina (NC) has the largest state population using private well water, the researchers studied live births in NC that occurred from 2003-2015. From birth certificates, they could collect each pregnant person’s address at the time they delivered their babies. The researchers also used the NC-WELL database, which is a database of over 100,000 geocoded well water tests conducted from 1998-2019 from almost all census tracts in North Carolina. These tests include measurements of the concentrations of metals. The NC-WELL database allowed the researchers to assign each pregnant person’s address an estimate of their exposure to private well water and the concentrations of metals measured in that well water. Ultimately, the study included over 1.3 million births. This large sample size allowed the researchers to determine if increased metals in well water was associated with preterm birth.

The study found that people living in census tracts where over 25% of NC-WELL water tests exceeded EPA’s safe standard for cadmium had 11% higher odds of preterm birth than people who did not. People living in census tracts where over 25% of NC-WELL water tests exceeded EPA’s safe standard for lead had 10% higher odds of preterm birth than people who did not. These results indicate that cadmium and lead in private well water were each associated with preterm birth.

The study then modeled how the exposure to mixtures of metals was associated with preterm birth. This is particularly important because few studies assess the risks of multiple chemical exposures, even though it is highly likely people are exposed to more than one chemical at a time. When considering exposure to a mixture of seven metals present in private well water, the researchers found that exposure to the combination of cadmium and lead was associated with preterm birth.

In the US and NC, Black and Native American people have much higher rates of preterm birth than white people. Racial disparities in exposure to toxic chemicals could influence racial disparities in birth outcomes. As the study states plainly, “This is especially pertinent to consider when evaluating private well water-based exposure in NC, as structural environmental racism has led to poor and minority communities being more likely to rely on private well water.” This study found that when considering exposure to a mixture of seven metals present in private well water, the effect on preterm birth was most extreme for Native American people. It was associated with 20% higher odds of preterm birth for Native American people. The researchers say this disproportionate effect of metal exposure on preterm birth reflects the multiple environmental hazards and contaminants disproportionately forced on Native American people over several centuries. They also note that other studies have found that Native American pregnant people have higher levels of toxic metals in their systems than the national average.

This study used publicly available birth information and private well water testing to create a large cohort to study the effects of metals in private well water on preterm birth. The results make clear that private well water needs more regulation in order to ensure the levels of dangerous metals like cadmium and lead do not put people at risk. The results also make clear that not all people bear the same risks of exposure or health effects of exposure. People of color bear a disproportionate burden because they are more likely to receive private well water, which may contribute to disproportionate rates of preterm births.

For more information, CHEJ has previously written about the health effects of leadcadmium, and the importance of considering the health effects of exposure to mixtures of chemicals.

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Cyanide

Cyanide is a chemical usually found in compounds with other chemicals. Cyanide compounds can be

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Using Scientific & Technical Information to Win

Photo credit: Milwaukee Area Technical College

By Stephen Lester.

I’m often asked what it is that I do at CHEJ. As a trained scientist, I provide technical assistance to grassroots community groups. People send me their environmental testing data to review. This data spans chemicals found in their drinking water, the air behind their child’s school or spouse’s factory, or the soil in the park where their children play. They ask me to do this primarily because they want to know what the results mean. But they also believe that if they gather enough information – the “right” information – and put it into the hands of the right decision-makers, they will do the right thing.  

So what do you think? True or false? Is information power? Can you solve your environmental problem(s) this way? No, you cannot. By itself, information is not power. It’s not the information but rather what you do with it that makes all the difference in the world. Just gathering data and sharing it no matter how important or impactful will likely not change a bureaucrat’s or a politician’s mind. But if you use the information in a thoughtful and strategic way, whether it’s to educate your community or others, and then to target the bureaucrats and politicians with a set of specific demands, you have a much greater chance to succeed. 

At CHEJ, we work directly with community leaders to help them become knowledgeable and proficient in understanding the technical, health, statistical and scientific aspects of chemical exposures. We also work with community leaders to help them understand how to use technical information to achieve their goals and win what their community needs to resolve. What we do includes reviewing testing data; cleanup plans; technologies for treating/disposing of hazardous waste and household garbage; reviewing plans to build new facilities; defining a community-based testing plan that includes where to test, what to test (soil, air, water), what to look for; evaluating a health study completed by a government agency or other entity; and so much more. CHEJ also has more than 50 guidebooks and fact-packs on a wide range of topics that you can use to focus your group on what it needs to be successful.

So don’t get trapped into believing you can win by gathering information, or become frozen into inaction until you gather a bit more information. What really matters is what you do with the information you have and how it strategically fits into your organizing plan. 

To learn more about CHEJ’s technical assistance services, see our website at http://chej.org/assistance/technical-assistance/.

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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.

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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Cyanide

Cyanide is a chemical usually found in compounds with other chemicals. Cyanide compounds can be

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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.

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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Cyanide

Cyanide is a chemical usually found in compounds with other chemicals. Cyanide compounds can be

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