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 to environmental chemicals. These features include the timing and vulnerability of exposures, exposures to mixtures, effects at low doses and genetic alterations called epigenetics.
Traditional thinking tells us that how much of a chemical you are exposed to (the dose) determines the effect. This principle assumes that chemicals act by overwhelming the body’s defenses at high doses. We’re learning now that this principle is not always accurate and its place in evaluating risks needs to be reconsidered. What we now know is that some chemicals cause their adverse effects at low exposure levels that are not predicted by classic toxicology.
Recent research has shown that environmental chemicals like dioxin or bisphenol A can alter genetic make-up, dramatically in some cases. These changes are so powerful that they can alter the genetic material in eggs and sperm and pass along new traits in a single generation, essentially by-passing evolution.
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. That’s no longer the case.
This new field – called epigenetics – is perhaps the fastest growing field in toxicology and it’s 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.
What 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 blue eyes, or their susceptibility to diseases such as adult on-set diabetes, or to the development of lupus.
The environment is a critical factor in the control of these packaging processes. We may be born with our genes, but epigenetics changes occur because of environmental influences during development and throughout life. These influences include 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.
Epigenetics may explain certain scientific mysteries, such as why certain people develop diseases and others don’t, 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.
For more information see
https://www.healthandenvironment.org/environmental-health/social-context/gene-environment-interactions
Tag: pollution
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Historic Coal Ash Cleanup in PA
Four environmental groups today announced an historic agreement to reduce toxic pollutants leaking from a power plant’s coal ash dumps into groundwater and the Susquehanna River, the largest Chesapeake Bay tributary.
“This enforcement action is one of historic proportions, since it’s the largest penalty ever assessed at a coal ash pollution site in Pennsylvania history,” said David Masur, Executive Director of PennEnvironment. “We are glad to see DEP working with citizen groups to reach this important settlement for the good of the Commonwealth.” Read more.
On Tuesday, excavation began on the WDE Landfill in Andover, Minnesota, where toxic waste has been locked up since 1983. The landfill has been leaching hazardous chemicals into the surrounding environment since then, as testing found that the landfill lining was leaking. <Read more>
by Kenia French, CHEJ Communications Intern
A study from the University of Victoria found that humans likely consume 74,000-114,000 microplastic particles per year. How does this happen, and what does this mean for our health?
What are microplastics and where do they come from?
Every year, between 5 and 14 million tons of plastic flow into our oceans, and for a long time, we believed that it just stays there. You may have heard of the Great Pacific Garbage Patch: an expanse of plastic litter larger than Texas floating in the middle of the Pacific ocean. In fact, wherever there’s a major ocean in the world, there’s also a massive garbage island sitting in the middle.
However, recent research suggests that these large expanses of plastic don’t just simply sit there: they degrade over time. This degradation has resulted in a phenomenon referred to as microplastic, or tiny particles of plastic smaller than 5 millimeters, often microscopic. These tiny particles of plastic have infiltrated not only our oceans, but all of the water systems on our planet.
Why are these tiny plastic particles so bad for marine ecosystems?
Microplastic pollution is particularly dangerous because it has a particle and chemical aspect. Microplastics have been found in over 114 aquatic species. Plastic particles fill fish’s stomachs and clog their organs, which has been linked to disrupted eating patterns and starvation. Filter feeders (think oysters) are particularly impacted because their feeding mechanism involves sifting tiny, microscopic organisms out of ocean water— microplastics inevitably get caught up in their dinner.
Microplastics have the potential to leach dangerous chemicals, like PCBs or BPA. While PCBs have been banned in the US since 1979, they aren’t banned worldwide, and many find their way into the ocean through illegal dumping or countries with less stringent regulations. These chemicals have been linked to liver and reproductive damage in many fish species, and to accelerating the destruction of coral reefs.
If microplastics are having their largest impact on marine life, how do they affect people?
The good news is that most microplastics that affect sea animals don’t make it back to affect humans. Microplastics remain in fish gut tissue, and haven’t made it to the muscle tissue, which is what we eat.
As the University of Victoria study found, though, it is clear that we are consuming an astounding number of microplastics from our everyday foods. Seafood is not the only vector for contamination: they found that tap water, bottled water, and sugar, are just a few sources of human microplastic consumption.
Should we be concerned about the potential impact of microplastics on our health?
According to the National Geographic, dosage is a key concept in toxicology. While 74,000-141,000 may seem like very large numbers, they may be quite small in terms of microplastic toxicity and may not be enough to have any impact on human health. Consuming plastic doesn’t really sound healthy, but everything is relative, and there isn’t yet any evidence linking microplastics to human health problems.
How can I limit my impact on microplastic pollution?
What is clear now is that plastic consumption is a problem for species that live on our planet, especially ocean species. If these plastics are harmful for our oceans, then they are probably aren’t the best thing for us to consume either.
There are alternatives: scientists have discovered ways to create biodegradable plastics, and people can push for bans on plastics responsible for leaching toxic chemicals, like our PCB ban. Overall, the best thing for a person to do to reduce plastic pollution is to try to limit your consumption of single use plastics. Single use plastics are plastics you only use once: plastic bags, like the ones your groceries are bagged in, are the main culprit, but plastic water bottles and product packaging are significant sources as well. Next time you’re at the grocery store, choose a paper bag, or better yet— a reusable one!
This is the question that journalist Jim Daley raised recently in an article published in Scientific American. According to the article, the U.S. Environmental Protection Agency (EPA) is substantially changing the program that evaluates the toxicity of chemicals by shifting staff and program emphasis from the Integrated Risk Information System (IRIS) to duties related to implementation of the Toxic Substances Control Act (TSCA). Daley writes that “Former EPA officials contend that the shake-up takes chemical assessments out of the hands of career scientists, potentially to the detriment of public health.”
As evidence of this shift, Daley writes that that the agency has reduced the number of its ongoing chemical toxicity assessments from twenty to three.
The IRIS Program began in 1985 to support EPA’s mission to protect human health and the environment by identifying and characterizing the health hazards of chemicals found in the environment. The IRIS program has become the most respected scientific program in the agency. Its health assessments are the backbone of EPA risk analysis work and is the preferred source of toxicity information used by EPA to determine public health risks. It is also an important source of toxicity information used by state and local health agencies, other federal agencies, and international health organizations.
The TSCA program on the other has a much narrower focus which is primarily on reporting, record-keeping and testing requirements, and restrictions relating to chemical substances and/or mixtures, according to EPA’s website. Certain substances are not covered by TSCA including food, drugs, cosmetics and pesticides. While the 2016 amendment to TSCA greatly improved this regulation, it did not address its narrow focus. This shift began with the leadership of Andrew Wheeler who took over for a beleaguered Scott Pruitt as administrator of EPA in July 2018.
One EPA official who declined to be identified was quoted in the Daley article saying that IRIS and TSCA are “very different” in their approaches to evaluating the public health risks posed by exposure to chemicals. “One could make the argument that this is political interference, in that high-level people are saying which methodology we should be using to assess the safety of a chemical. “And the policy’s pretty clear that they’re not supposed to do that.”
Bernard Goldstein, Professor Emeritus at the University of Pittsburgh School of Public Health, who served as EPA Assistant Administrator of the Office of Research and Development (ORD) from 1983 to 1985, summed it up this way in the Daley article, “I really see this as part of a restructuring of EPA in such a way that science will have very little to do with what EPA is basing its regulation on, and that we will end up with much weaker regulations in terms of protecting public health. “It’s troubling, in large part because it’s very consistent with an overall approach – a very astute approach – to take out the inconvenient facts.” Also cited in the same article was a comment by Thomas Burke from the Johns Hopkins Bloomberg School of Public Health, a former EPA lead scientist adviser and Deputy Administrator of ORD from 2015 to 2017, “’any reduction’ of the number of IRIS chemical assessments ‘is a loss for public health and, unfortunately, puts populations who are exposed at risk.’”
Read the full article here.
A new elementary school in Moore County, North Carolina, is to be constructed between two Superfund sites threatened by high levels of air pollution, NC Policy Watch reports. According to the city, the site bears no heightened risk of contamination, but CHEJ science director Stephen Lester isn’t so sure. Stephen shares CHEJ’s findings that there is no scientifically proven “safe distance” from pollution sites, and he calls into question effectiveness of current school siting guidelines. He recommends that parents sending their kids to the new Aberdeen elementary school in the future be incredibly vigilent about changes in their children’s health.
The Moore County case is particularly relevant because the new Aberdeen elementary school would serve primarily low-income students and students of color. In many ways, constructing a new elementary school is a push toward progress, as existing Aberdeen elementary schools were built during the segregation era. However, the new elementary school’s future location could potentially mean disproportionately exposing students of color and low income students to environmental contamination. As Stephen says, children are at higher risk for health complications from pollution contamination, and no child should have to face health complications due to pollution. <Read more>
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Jayne DePotter spent almost a decade making her Michigan jewelry studio a second home for young artists seeking direction, seniors looking to exercise their hands and minds and new immigrants in search of community. <Read more>.
If the public is going to have a robust debate about the merits of fracking, both sides need to know what’s being pumped into the ground. <Read more>.
The Environmental Protection Agency plans to change the way it calculates the future health risks of air pollution, a shift that would predict thousands of fewer deaths and would help justify the planned rollback of a key climate change measure, according to five people with knowledge of the agency’s plans. <Read more>