Friday, December 15, 2017

EPA’s first endocrine disruptor tests show varied results

The U.S. Environmental Protection Agency’s newly released reviews show mixed results for Tier 1 screening of the first 52 pesticide chemicals in its Endocrine Disruptor Screening Program, launched to determine if these natural and synthetic substances impact human hormonal systems. 

Exposure to endocrine-disrupting chemicals – which interfere with any aspect of hormone action – may occur via pesticides, pharmaceuticals, personal-care products, and environmental pollutants, among others, and have resulted in a range of human diseases and abnormalities, according to the Endocrine Society. 

Specifically, the EPA said that the first 52 chemicals screened were not selected because of their potential to interact with endocrine systems, but rather for their potential for human exposure. 

“It is important not to equate a chemical’s bioactivity with the conclusion that the chemical harms the endocrine system in humans and wildlife,” the EPA said. “Bioactivity is an indicator that a chemical has the potential to alter endocrine function, but without further testing, one cannot determine (1) whether the chemical actually alters endocrine function and (2) whether that altered function produces an adverse outcome in humans and animals.” 

The EPA’s Tier 1 screening data are the best way for the agency to determine whether an EDC has the potential to interact with the estrogen, androgen or thyroid hormonal systems and if they then require Tier 2 or more thorough testing. 

These first reviews are “an important step in a multi-step process to protect public health and the environment by ensuring that exposure to chemicals does not result in adverse effects that can occur from the disruption of hormones,” the agency said. 

The EPA pulled the first 52 chemicals from a revised List of the EDSP Universe of Chemicals, a document that initially contained some 10,000 chemicals. The agency prioritized these chemicals for screening by considering physical chemical properties, exposure, and an effect-based approach using advanced computational toxicological methods.

Of the first 52 chemicals evaluated, 18 chemicals showed potential interaction with the thyroid pathway; 17 of them with the androgen pathway; and 14 also potentially interacted with the estrogen pathway, the agency reported. 

The EPA also found “there was no evidence for potential interaction with any of the endocrine pathways for 20 chemicals.” However, 14 chemicals showed potential interaction with one or more pathways, though the EPA said it “already has enough information to conclude that they do not pose risks.” 

More screenings will take place as the EPA recommended a comparative thyroid assay for four chemicals that showed interaction with the thyroid pathway in mammals; a medaka one-generation reproductive test for 13 chemicals that showed interaction with the estrogen or androgen pathways in wildlife; and a larval amphibian growth and development assay for five chemicals that showed interaction with the thyroid pathway in wildlife. 

“This will help us better understand the potential of these chemicals to cause adverse effects through interaction with the endocrine system,” the EPA said.