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Category: Toxic Tuesdays

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Selenium

Toxic Tuesdays

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

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Selenium

Selenium is a mineral found in most rocks and soil across the globe. It can be extracted and processed from rock for commercial and manufacturing uses. About half of the processed selenium in the world is used in glass production. Another large portion of processed selenium is used in electronics, such as batteries, solar cells, and photoconductors, and the production of rubber, plastics, paints, and inks.

Selenium can be released into the environment via the manufacturing or disposal process, thereby entering water and topsoil. People can then become exposed by drinking selenium-contaminated water or eating contaminated agricultural products. Selenium also bioaccumulates in fish, meaning people may be exposed to harmful levels of selenium even if they do not live near a manufacturing or disposal site. Short-term oral exposure to high levels of selenium can cause nausea and vomiting. Long-term oral exposure can cause a disease called selenosis, which can include gastrointestinal dysfunction, neurological dysfunction, hair loss, and sloughing off nails. In extreme cases, selenosis can even cause cirrhosis and death. Selenium dust can also be released into the air when burning oil or coal. This can cause coughing, bronchitis, and irritation of the respiratory tract, which can make it difficult to breathe.

While trace amounts of selenium are required to maintain human health, short- or long-term exposure to high amounts of selenium are dangerous. There are many examples from around the world of people, fish, and birds being poisoned by selenium. With its diverse array of commercial and manufacturing uses, it is crucial that protections be put in place to ensure that people are not exposed to it.

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Ethlybenzene

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

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Ethylbenzene

Ethylbenzene is a colorless flammable liquid that comes from coal tar and petroleum. It is primarily used to synthesize chemicals that are used in plastics. Ethylbenzene can also be used in fuels and injection fluid, which is used to release natural gas from the ground. It has industrial uses in solvents and pesticides and can also be found in consumer products like paint and ink. Spills and waste disposal from factories that use ethylbenzene often enter the water and soil. Burning oil, gas, coal, and cigarettes can release ethylbenzene into the air. Inhalation of this contaminated air is the primary path of exposure.

Brief inhalation of air contaminated with ethylbenzene can cause eye and throat irritation and dizziness. Little else is known about the human health effects of short- or long-term exposure to the chemical. In scientific studies of laboratory animals, short-term exposure has been shown to cause permanent hearing loss; long-term exposure has been shown to cause kidney damage too.

The International Agency for Research on Cancer says that ethylbenzene is a possible human carcinogen, meaning it might cause cancer in humans. While more studies could be done to better understand the effects of exposure on humans, it is clear ethylbenzene is a biologically dangerous chemical, and there should be protections in place to ensure that people are not exposed to it.

 

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Benzo(a)pyrene (BaP)

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

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Benzo(a)pyrene (BaP)

Benzo(a)pyrene (BaP) is a compound in a group of chemicals called polycyclic aromatic hydrocarbons (PAHs). PAHs like BaP are formed in the incomplete burning of coal, oil, gas, or other organic matter. Once formed, they can enter the air, water and soil. The most common way people are exposed to PAHs is by inhaling contaminated air. Vehicle exhaust, wood smoke, asphalt paving and agricultural burning can expose people to PAHs like BaP.

Exposure to BaP for even short periods of time can affect blood cells, leading to anemia and immune system defects. Exposure for long periods of time can affect function of the reproductive system. In studies of laboratory animals, prenatal exposure to BaP impaired learning and memory of offspring.

The most widely known effect of BaP exposure is cancer, and links between BaP and cancer have been known since the 1970s. BaP is one of many components of tobacco smoke that can cause lung cancer. BaP is dangerous because the body converts it into other compounds that can permanently change our cells’ DNA. This can cause cells to function improperly leading to cell death, abnormal cell growth, tissue damage and/or cancer.

CHEJ has previously written about PAHs here.

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Exposures to Chemical Mixtures Matter​

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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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Total Petroleum Hydrocarbons (TPHs)

Toxic Tuesdays

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

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Total Petroleum Hydrocarbons (TPHs)

Total petroleum hydrocarbons (TPH) are a family of hundreds of chemicals that come from crude oil. When crude oil is spilled during extraction or processing into petroleum products, TPHs can contaminate the environment. Because TPHs contain so many chemicals, it can be impractical or impossible to measure each individual chemical. Instead, total concentrations of TPHs are measured at contamination sites. Upon contaminating soil, some TPH components will remain there for a long time without breaking down. Upon contaminating water, some components will form films on the surface while others will sink to the bottom. Touching contaminated soil or drinking contaminated water can lead to exposure to TPHs. Because many products and gasolines are derived from crude oil, almost everyone has some exposure to TPHs even in the absence of a chemical spill. For instance, breathing the air at gas stations or using certain pesticides can cause exposure to TPHs.

Exposure to TPHs can have effects on the nervous system, causing headaches, dizziness, or numbness in the extremities. Some TPH chemicals can also affect the blood, immune system, respiratory system, and skin. In laboratory studies on animals, TPH exposure was also found to affect liver function, kidney function, and fetal development. Furthermore, at least one TPH chemical – benzene – is known to cause cancer in humans. Despite known health effects of exposure to TPHs, and the potential for synergistic effects of simultaneous exposure to multiple TPH chemicals, there are no federal regulations specific to TPHs.

CHEJ has previously written about the health effects of some chemicals commonly found in TPH and communities that have been exposed to them: benzene, naphthalene, toluene, and xylene.

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Glycophosate

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

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Glyphosate

Glyphosate is a chemical found in weed killer products such as RoundUpTM used on farms and home lawns. It gets absorbed by plant leaves, stopping plant growth within hours. Because of its effectiveness, glyphosate is found in widely used products that are easily obtainable. It is used all over the United States, but its highest concentrations are in the Midwest and Plains states. When glyphosate-containing weed killers are sprayed to kill plants, it can be inhaled and get on the skin. This can cause skin irritation and respiratory effects. People frequently working with glyphosate may be more likely to develop these respiratory effects. In scientific studies on animals, exposure to glyphosate during pregnancy caused developmental defects in the resulting offspring. Furthermore, there is concern that when combined with other chemicals found in weed killer products, glyphosate may have increased toxicity on humans.

Whether or not exposure to glyphosate increases the risk of cancer is inconclusive. The US EPA classifies it as not likely to cause cancer; however, the International Agency for Research on Cancer (IARC) concluded that it probably does. There have been allegations that large agrochemical corporations that use glyphosate in their products have close relationships with the governmental organizations that conduct the studies regarding glyphosate’s health risks. While more studies and risk assessments may need to be done to be certain of the risks, it is crucial that these studies are done transparently and without bias to protect and inform the public.

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Transgenerational Toxicity

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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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Polybrominated diphenyl ethers (PCBEs)

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

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Polybrominated Diphenyl Ethers (PBDE)

Polybrominated Diphenyl Ethers (PBDE) are chemicals that are flame retardants – meaning they are added to different materials to make them less susceptible to fires. PBDEs are found in various everyday materials, such as furniture padding, computers, rugs, and electrical wires. They are a synthetic (not naturally found in the environment) subset of the organobromine compounds, chemicals where a carbon molecule is bonded to a bromine molecule. There are 209 different forms of PBDEs, which vary based on what the carbon-bromine structure looks like.

PBDEs were discovered in the 1970s, and since then, several of them have been phased out of production (PentaBDE and OctaBDE), but other versions (such as DecaBDE) are still being manufactured. While some states, such as California and Washington, have banned specific forms of PBDEs from production, there is no national restriction on the production of this chemical as of 2023. It’s also important to note that even for PBDEs that have been banned or phased out of production, the waste from production and manufacturing remains in the environment and causes harm.

The lack of national attention to this class of chemicals is concerning because of the mounting evidence that PBDEs have negative impacts on human health. For example, these chemicals are thought to be endocrine-disrupting. The endocrine system, which oversees the regulation of hormones, is vital to human health. When this system is damaged, it can cause various adverse health effects, such as cancer, reproductive damage, and neurological damage. A case-control study found that exposure to PBDEs was associated with an increased risk of breast cancer among post-menopausal women. Another study found that the BDE-28 compound was associated with an increased risk of papillary thyroid cancer. As for reproductive health, a study on infants reported that pregnancies that had PBDE chemicals in the umbilical cords, those infants were more likely to have lower birth weights. And a chemical that causes fetal abnormalities is called a teratogen, although PBDE does not carry this classification by the Environmental Protection Agency. Evidence of neurological damage has also been in animal studies, where PBDE was found to cause neurotoxic effects on memory, attention, and leaning ability.

Exposure to PBDEs during pregnancy is only one route of exposure to this chemical. Because PBDEs decompose slowly in the environment, they bioaccumulate and build up in the food chain. Fish and other marine life are especially prone to bioaccumulation. Thus, PBDE contamination could be of concern for people who consume a lot of seafood or rely on it as their primary protein source. Another way that people can be exposed to the chemicals is through water. PBDE waste can seep through the ground and contaminate the groundwater sources. Another exposure route, which accounts for an estimated 80% to 90% of exposure for the population, is inhaling contaminated dust particles. For example, PBDE can be found in the dust that accumulates in homes. One study found that individuals who had higher levels of PBDE in the dust at their houses had higher levels of the chemical in their blood serum levels.

PBDEs are considered persistent organic pollutants (POP), and many communities are fighting against this contamination in their backyards. For example, the Alaska Community Action on Toxins (ACAT) has been advocating for years to ban the use of PBDEs in the state. Another group that has been advocating for the ban on PBDEs are first responders, specifically fire-fighter organizations. When blood samples were taken from firefighters, they had brominated dioxins and furans in their bloodstreams. Fire fighters are more exposed to these chemicals because when a house fire occurs, all of the products that have PBDEs in them, such as furniture upholstery, burn up and release these toxic chemicals into the air that the first responders breathe in.

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Isobutylene

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

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Isobutylene

Isobutylene is a colorless gas that comes from natural gas. Its highly reactive nature makes it useful in the synthesis of many products including gasoline, rubber, plastics, resins, and other chemicals. Little toxicity information is known about isobutylene, and no occupational exposure limits are established, but exposure can cause irritation, headache, dizziness, and fatigue. The most dangerous feature of isobutylene is that it has a flash point of -80°C, meaning that above this temperature, it can ignite. As isobutylene is often in the presence of other flammable chemicals, isobutylene ignition can cause large explosions.

On February 3rd, 2023 a Norfolk Southern freight train derailed in East Palestine, Ohio. Twenty of the derailed cars contained hazardous chemicals, including isobutylene. Some cars released these chemicals into the surrounding air, soil, and water. On February 6th, Norfolk Southern made the decision to conduct a controlled burn of some of the remaining chemicals. Nearby residents were evacuated because of the health hazard of inhaling the smoke fumes. In addition to the fumes, release of chemicals into the surrounding environment could cause serious health problems. The Ohio Department of Natural Resources found that over seven miles of stream were affected by the chemical spill and thousands of fish died, raising concerns about dangers to residents in a large radius surrounding the spill. EPA ordered Norfolk Southern to identify and clean up contaminated soil and water. However, secrecy surrounding the scale of the accident and a reluctance to test thoroughly for all chemicals of concern has frustrated residents. EPA must prioritize the health of East Palestine residents and work transparently with them to identify and remediate the effects of this train derailment, chemical spill, and fire.

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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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