Low Dose Toxicity of Endocrine Disrupting Chemicals

At Sprout, we’ve always worked to raise awareness about the dangers that endocrine disrupting chemicals (EDCs) can have on our developing children. Scientists are still identifying these chemicals in our environment and in our products. A recent report even found that prenatal exposure to EDCs in personal care products can speed up puberty in girls (read our article on the report).

Studies continue to show proof that exposures to EDCs are associated with human diseases and disabilities. Even more alarming is the fact that endocrine disrupting chemicals are harmful to human health at extremely low doses.

What’s an extremely low dose? How small are we talking about?

Studies have discussed seeing effects at levels of 1 part per billion, or even 1 part per trillion. But how much is that? What does that mean? Here are a few examples to help you picture it.

1 Part Per Billion is:

  • A Single Drop of Water in an Olympic-sized Swimming Pool
  • One Second out of 32 YEARS
  • One Foot of the Distance to the Moon.
  • One Penny in TEN Million Dollars.
1 Part Per Trillion is:

  • One Thousand times Smaller than 1 part per Billion
  • A Single Grain of Sand in an Olympic-sized Swimming Pool
  • One Second out of 32,000 YEARS

Warnings of the Harms of EDCs came in 2009 and 2015

The Endocrine Society put out two papers on this subject, the first in 2009, then another in 2015. Their Scientific Statement on Endocrine-Disrupting Chemicals warns how exposures to EDCs in both animals and humans, especially during development, may lay the foundations for disease later in life.

Evidence of EDC harm at low doses


An EWG investigation into atrazine (a heavily-used weed killer sprayed primarily on corn) revealed the harm that can result from very low doses of harmful chemicals. Atrazine is an EDC that can affect both animals and humans. It disrupts hormones and harms the developing fetus. (It can even turn developing male frogs into egg-laying females.) The paper describes studies of pregnant women who drank water contaminated with atrazine. They were more likely to have premature or low-birth-weight babies which increases the risk of health problems later in life, including breathing problems, developmental delays, and cardiovascular disease. Atrazine in drinking water is regulated by federal law, but these harmful effects have been seen at levels lower than the federal limit of 3 parts per billion.

Testosterone Disruption

In utero, a mouse gets hormones from his mother, makes some himself, AND he gets some from his neighbors. The sex of his neighbors influences his development. When he is located between two males, he gets just a little more testosterone. How much more? Less than 1 part per trillion. (1 part per billion is 1 drop in an Olympic-size pool, 1 part per trillion is 1000 times smaller than that!) And this small amount of testosterone can alter the size of his genitals and even his fertility as an adult. Extremely small changes in testosterone at critical periods can cause significant changes in development. Read more in our article, Stealth Chemicals: A Talk by Dr. Shanna Swan of the Children’s Environmental Health Center.

Study by The National Center for Biotechnology Information

The NCBI study, Hormones and endocrine-disrupting chemicals: low-dose effects tells us that, “For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of ‘the dose makes the poison,’ because EDCs can have effects at low doses that are not predicted by effects at higher doses.

Here are a few more of the many noteworthy findings of the study:
  • BPA at rate of under 400 g/kg has shown a negative effect in people on the prostate, mammary gland, brain development and behavior, reproduction, immune systems.
  • Methyl paraben—used as a preservative in personal care—was found to have estrogenic effects at less than 1000 mg/kg in the uterine tissue organization of animals.
  • Triclosan—an antibacterial agent still in many toothpastes—showed estrogenic activity at less than 12 mg/kg causing an altered uterine response in animals.

Why understanding the dosage of endocrine disrupting chemicals is so important

One example is thyroid function in pregnant women. The NCBI report states that even small deficits in circulating thyroid hormone in pregnant women can cause cognitive deficits in their children. Thyroid hormone in developing children is essential, so identifying the dose at which these events occur is critical.

There are several biological reasons why hormones can be affected at such low doses. Even slight changes in hormone concentration can generate significant changes in the human body.

A report out of Tufts University (When the dose doesn’t make the poison: low dose effects & endocrine disrupting chemicals) analyzed medical research papers and identified at least 28 chemicals with low dose effects. This is a big increase in the number of known chemicals with low dose effects compared to the 4 chemicals that were found in a 2002 study.

More studies and better oversight needed

Many EDCs have not been tested at low doses. Fundamental changes in chemical testing and safety determination are needed to better understand how to predict these changes, limit our exposure, and protect ourselves and our children.

Clearly more research is needed to identify EDC’s and their harmful effects at low doses. The best practice is to avoid contact with EDC’s whenever possible. Sprout San Francisco, is dedicated to providing products are that are safe, organic, and free from harmful chemicals.