Scientific Evidence to Support 'Seven Generations' future thinking; our toxic chemical exposures may harm our great-grandchildren

Native American tribes hold dear the concept of seven generations planning, that the impact of decisions should be considered out seven generations into the future, about 150 years. The idea is that our decisions today should consider the potential benefits or harm that would be felt by seven future generations. While such future-thinking has obvious ethical and moral value, it seems that it may also have scientific validity.

A recent article by Washington State University biologist, Dr. Michael Skinner and his scientific team provides evidence from rat studies that male infertility can result from an exposure to the pesticide vinclozolin. What’s the catch? The pesticide exposure was not to the infertile rat, but to its great grandmother, three generations earlier!

But, this wasn’t Skinner’s first article on the subject. Around 2005 he tripped over this astounding observation almost by accident, when the pups of pregnant rats exposed to vinclozolin were accidentally bred out several generations. That’s when Skinner and his colleagues learned that all of the pups for the next four generations - that is, even the great-grandchildren of the exposed rats - had abnormally low sperm counts!

Michael Skinner and his colleagues repeated the experiments many times, and tested other chemicals – including those found in plastics (Bisphenol-A or BPA, DEHP, and other phthalates), pesticides (vinclozolin, methoxychlor, permethrin, and tributyltin), industrial chemicals (dioxin, jet fuel mixes) and nicotine - that lead to other diseases of the prostate, kidney, ovaries, brain and behavioral deficits, reproductive tract abnormalities, and immune system abnormalities. Over and over they found the diseases in animals that were four and even five generations away from the original mothers that had been chemically-exposed during pregnancy. (see published data here and here)

There is a scientific explanation for these ‘transgenerational’ effects. The explanation is ‘epigenetics’ – things that affect the function of DNA – the genetic code - but without altering the DNA itself. Skinner and his team discovered that portions of the DNA had additional methyl groups – a carbon and three hydrogen molecules, written as CH3 – that alters the ability of a gene to be turned on or off. Start messing with the ability of the genetic code to function and you’ve really got a problem. Transgenerational epigenetic inheritance, including abnormal DNA methylation, has been implicated in different types of cancer, heart disease, kidney disease, obesity and other diseases. And, it’s not just humans that are at risk. Transgenerational epigenetic inheritance has been implicated in diseases of animals, of plants, and even bacteria and fungi.

See this month’s excellent Smithsonian Magazine story about Dr. Skinner and his discoveries here and a scientific commentary in Environmental Health Perspectives here.

The good news is that transgenerational epigenetic science is catching on; the search term brings up hundreds of articles published in scientific journals. More good news is that the government is paying attention too. The National Institutes of Environmental Health Sciences (NIEHS) up $3 million to support academic research going out for three generations, focused on the mechanism by which these effects happen, and which environmental pollutants have transgenerational effects. Also, many of the studies to date have tested rats at much higher doses (adjusted for body weight) than people are exposed to, so a wider range of doses will have to be explored.

The bad news is that our chemical risk assessment process is way behind. Chemicals are reviewed and approved for commercial uses with no requirement for any toxicity data past first generation effects, and even that is a relative rarity. Industrial chemicals are often approved with no data at all.

But, maybe the biggest problem is that many of the political and/or corporate persons in positions of power that should be listening to what science says are willfully deaf to scientifically discovered truths because these may end up challenging their ideological perspectives, usurping their positions of privilege, or negatively affecting their economic ‘bottom line’. (see as examples documentation by David Michaels and my own ‘Delay Game’ report)

My friend and philosopher Fred Guerin pointed out, after reading the Smithsonian Magazine story, that, “Michael Skinner’s findings, (as Alexander Fleming’s and Madame Curie’s) were not entirely predicted or intended but, rather, the result of a serendipitous accident. In other words, his results reflect an authentic desire to discover the truth of things; they are not the product of what often passes for genuine research but are nothing more than the tortured scientific reasoning solicited and paid for by those corporations or persons who stand to gain most by distorting truth to defend their toxic chemical products.” Well stated, Mr. Guerin. 

The Toxic Substances Control Act (TSCA) enacted in 1976 is in desperate need of being replaced with a chemical policy that protects human health and the environment, and promotes a market shift towards less-toxic and non-toxic products and processes. The proposed bill S. 1009: The Chemical Safety Improvement Act (CSIA) now before the Senate of the U.S. Congress will not do that, as currently written. Maybe that is why it is being criticized by environmental public health groups, but supported by the chemical industry and its trade association, the American Chemistry Council (ACC).

Seven generation thinking makes sense! I look forward to chemical risk assessments, regulations, and laws that reflect this fact.

About the Authors

Jennifer Sass

Senior Scientist, Federal Toxics, Health and Food, Healthy People & Thriving Communities Program

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