Image Credit: Kristen Seim

Jane eats organic foods, avoids plastic containers and switched to plant-based shampoo and cosmetics.  “You have no idea how clean my home is, but I still don’t feel protected,” Jane told me.

Like many other expectant mothers, Jane is stressed about protecting her baby’s health.

We all have reasons to be worried about man-made chemicals in our environment, even if we are not expectant mothers. Over the past decade, attention-deficit hyperactivity disorder has increased by 30 percent and autism spectrum disorders have doubled. Over the past 30 years, obesity has doubled in children and quadrupled in adolescents [1]. Of course, many factors contribute to these pandemics, including improved diagnostic techniques, changes in diets and physical activity, etc. But cumulative evidences have suggested that these factors alone cannot explain the whole phenomenon. Phthalate exposure and organophosphate pesticides have been associated with higher ADHD risks [2-3]. Prenatal and perinatal chemical exposure to organic pollutants and pesticides have been linked to childhood obesity [4].

As Linda S. Birnbaum, the Director of the National Institute of Environmental Health Sciences put it, “Clearly we must look to the environment as the primary cause of such increases because the human genome has not changed.” [1]

Although the FDA regulates thousands of chemicals in food and drug products, the regulation of industrial chemicals falls to the EPA. Over 80,000 chemicals were introduced to the market and available for use since 1976 when Toxic Substances Control Act (TSCA) was passed. [5] 700 that were previously not found in humans are now measurable in adult’s body. [6]

 

Figure 1 ~ Industrial chemicals testing in the U.S. Image Credit: Kristen Seim.

How many of them are required to be tested for safety? Only 300 (Figure 1). And how many of them does TSCA restrict? Fewer than 20. [7]

The “safety measures” Jane was taking weren’t based on advice from her doctor. A Boston Globe[8] article last year reported that doctors didn’t tell parents anything about environmental chemicals unless asked specifically because doctors have other life-threatening risks to discuss with expecting parents.  Doctors aren’t confident about their own understanding of the risks involved, and do not want to terrify them further with information about environmental chemicals.

The state of the science is unclear when it comes to linking chemical exposure to diseases. The gold standard for establishing causation is randomized controlled trials (RCTs), where people participating in the study are randomly assigned to one or other of the different “exposures.”

When it comes to environmental studies, scientists cannot assign people to be exposed to chemicals. It is morally indefensible. The fact that human beings are daily exposed to a cocktail of environmental toxicants, not a single one at a time, also makes it difficult to link diseases to specific chemicals.

A common alternative practice in science when RCTs cannot be done is to use the weight-of-evidence approach, where scientists review all animal toxicological tests, epidemiological studies and reach a consensus of how hazardous a chemical is and whether it is likely associated with the health outcome.

This approach does not come cheap. The EPA estimated that it costs $200,000 [9] to do this for one chemical. Under the current TSCA chemical manufacturers are usually not required to prove their products are safe. Rather, before a chemical can be regulated, the burden is on the government to prove that the chemical is harmful at levels people could be expected to encounter. Pharmaceutical drugs are assumed to be harmful until tested, but industrial chemicals are treated the opposite way. For example, the weight-loss drug Qsymia went through extensive reviews before FDA approval. Its maker is still required to conduct long-term studies to further evaluate safety.

In contrast, for example, plants manufacturing product plastics and resins have generated 2.2 million pounds of bis-phenol A (BPA) every year since 1960 [10-11]. BPA is not regulated by the EPA [12]. Workers exposed to high levels of BPA (urine BPA 57.9 µg/gCr) have higher risks of male sexual dysfunction [13]. The levels released into the environment are 100 times lower than these workers were exposed to [14], but trace amounts of BPA are now found in 90% of American adults [15], and the health consequences of this low, long-term exposure are unclear. We should therefore err on the side of caution and put measures in place to prevent the release of these chemicals into the environment, until better testing can establish safety (or not!).

Because of the large potential risks and large uncertainties around the effects of new industrial chemicals, the U.S. government’s “innocent until guilty” approach to regulation cannot assure the public that products they are exposed to are safe. Other governments err on the side of caution. The European Union, for example, requires manufacturers to prove that new industrial chemicals do no harm before they can be used in consumer goods [16].

Although the burden of proof is unlikely to shift from the EPA to industry in the near future, changes are on the way. In 2013, the U.S. Senate Committee on Environment and Public Works proposed reforms to TSCA, which requires the EPA to publish a list of chemicals of priority concern and require the submission of data on the chemicals [17] . However, bills have been stalled.

As Congress considers revisions to the TSCA, they should look to the stricter approval standards in other industrialized nations. A bill requiring mandatory pre-market testing of commercial chemicals would do more to safeguard public health, reducing the chance that newly introduced anthropogenic (human-created) chemicals will have harmful unintended effects on the general population.

Cindy X. Hu is a 3rd year graduate student in Environmental Health at Harvard T.H. Chan School of Public Health.

Any opinions expressed in this article are the opinions of the writer and not necessarily those of SITN.

References

[1] Birnbaum, Linda S. “When environmental chemicals act like uncontrolled medicine.” Trends in Endocrinology & Metabolism 24.7 (2013): 321-323.

[2] Kim, Bung-Nyun, et al. “Phthalates exposure and attention-deficit/hyperactivity disorder in school-age children.” Biological psychiatry 66.10 (2009): 958-963.

[3] Eskenazi, Brenda, et al. “Organophosphate pesticide exposure and neurodevelopment in young Mexican-American children.” Environmental health perspectives (2007): 792-798.

[4] La Merrill, Michele, and Linda S. Birnbaum. “Childhood obesity and environmental chemicals.” Mount Sinai Journal of Medicine: A Journal of Translational and Personalized Medicine 78.1 (2011): 22-48.

[5] http://saferchemicals.org/get-the-facts/what-is-tsca/

[6] http://www.chemicalbodyburden.org/whatisbb.htm

[7] U.S. Government Accountability Office. “Options Exist to Improve EPA’s Ability to Assess Health Risks and Manage Its Chemical Review Program.” http://www.gao.gov/new.items/d05458.pdf

[8] http://www.bostonglobe.com/lifestyle/health-wellness/2014/06/29/why-doctors-don-talk-pregnant-women-about-toxic-chemicals/FJKIHxcCNwYNHSoAmYzTqK/story.html

[9] U.S. Environmental Protection Agency. “HPV Chemical Hazard Data Availability Study. ” http://www.epa.gov/hpv/pubs/general/hazchem.htm

[10] http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/expert-answers/bpa/faq-20058331

[11] http://en.wikipedia.org/wiki/Bisphenol_A

[12] http://www.epa.gov/oppt/existingchemicals/pubs/actionplans/bpa.html

[13] Li, D., et al. “Occupational exposure to bisphenol-A (BPA) and the risk of self-reported male sexual dysfunction.” Human reproduction (2009): dep381.

[14] Hanaoka, T., et al. “Urinary bisphenol A and plasma hormone concentrations in male workers exposed to bisphenol A diglycidyl ether and mixed organic solvents.” Occupational and environmental medicine 59.9 (2002): 625-628.

[15] Centers for Disease Control and Prevention. “Fourth National Report on Human Exposure to Environmental Chemicals (Executive Summary).” http://www.cdc.gov/exposurereport/pdf/fourthreport_executivesummary.pdf

[16] http://ec.europa.eu/enterprise/sectors/chemicals/reach/index_en.htm

[17] https://www.congress.gov/bill/113th-congress/senate-bill/1009

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