By Kelly A. Reynolds, MSPH, PhD
Newly published research shows a significant increase in preterm birth rates in women exposed to phthalates, a commonly used group of chemicals sometimes found in drinking water. How phthalates contribute to preterm birth is currently unknown. Also unknown are the most relevant sources of exposure. Water is one possible route but additional sources may surprise you.
What are phthalates?
Also known as plasticizers, the primary use of phthalates is to make plastics more pliable. They are found in hundreds of products, including PVC pipes, medical tubing, flooring, adhesives, detergents, clothing, food containers, plastic wraps and personal care products (such as soaps, shampoos, hair sprays and nail polishes). There are at least 13 metabolites of phthalates excreted in urine, suggesting exposure in the general US population is widespread. The most commonly used phthalate is di-2-ethylhexyl phthalate, or DEHP. Adult women have higher levels than men, presumably due to increased use of cosmetics, body washes
What are the health risks?
Despite medical advances, preterm birth rates have been increasing over the last two decades. The cause of this increase is not known; however, environmental factors are a plausible cause. In a recent study, 482 pregnant women over a three-year time frame were evaluated for nine types of phthalate metabolites in their urine up to three times over the course of their pregnancy. Of the 482 test subjects, 130 (27 percent) delivered prior to complete gestation (defined as prior to 37 weeks). Those delivering preterm were found to have been exposed to higher levels of at least four types of phthalates: di-2-ethylhexyl phthalate (DEHP), mono-(2- ethyl)-hexyl phthalate (MEHP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) and mono-n-butyl phthalate (MBP). In fact, those exposed to the highest levels were up to five times more likely to experience a preterm birth.
Researchers are careful to warn that their study does not prove phthalate exposures cause premature birth, but there does appear to be an association, which means there is an indication that phthalate exposures somehow contribute to the adverse health outcome. For example, coffee drinkers tend to have higher rates of lung cancer. Coffee does not cause the lung cancer. Rather, the fact that many partake in smoking while having coffee leads to the adverse effect. In this example, smoking is causal, while coffee is associated with lung cancer. An understanding of the pathway of phthalates in the body and related side effects that might lead to preterm birth is critical to developing effective interventions. Not enough is known about phthalates and their role in preterm birth to justify any changes in prenatal care routines.
In addition to suspected pregnancy effects, exposure to phthalates may cause mild stomach ailments, nausea and vertigo in healthy populations. They are suspected endocrine-disrupting compounds and repeated exposure over time may lead to damage to the liver and testes, reproductive effects and cancer. Those at highest risk appear to be dialysis patients or hemophiliacs, where continued use of hospital tubing (the phthalate content is among the highest of any other type of plastics) leads to increased exposures. Scientists are uncertain about the health effects of phthalates at current environmental exposure levels. While the National Institute of Environmental Health Sciences (NIEHS) states that the majority of phthalate compounds pose minimal concern, the National Toxicology Program concluded that high levels of certain types may affect human reproduction or development.
How are people exposed?
Exposure assessment is a complicated science. Understanding the sources leading to exposure is only part of the issue. The frequency and magnitude of the exposure are also key factors. In addition, the site of contact has an influence on how much of the contaminant gains entrance into the body to initiate health effects. Further, once a person comes into contact with a contaminant, variables such as genetics, chronic illness, age and immune status (including pregnancy) have an impact on both exposure and health outcomes. Ingestion of food and drinks is thought to be the primary exposure route of phthalates, although phthalate-laden vapors or dust particles may also be inhaled. Once in the body, phthalates tend to break down quickly before being excreted in urine.
One study found that children were exposed to a significantly higher amount of phthalates, where adults in the upper range were exposed to 21 µg/kg/day, compared to 25 µg/kg/day for children. Previous studies suggest a reference dose (the recommended maximum to minimize health risks) was 20 µg/kg/day; well below the measured dose in children and also adults. DEHP was detected in premature neonates at a median value (median range: 42 µg/kg/day—upper range: 1,780 µg/kg/day), a potential cause for concern.
Are phthalates in water a major concern?
Pressures on the water treatment industry are mounting as improved monitoring technology results in increasing evidence of contaminants present. While no one wants chemical byproducts of potential health concern in the drinking water, the reality is that health risks are not well quantitated and water may be only a minor source of exposure. In regard to phthalates, higher exposures are likely from perfumes, deodorant and other personal care products. During a CDC survey from 1999-2000, phthalates commonly found in fragrances were detected in the highest concentration in human biomarkers.
In water, US EPA has set a maximum contaminant level goal (MCLG) for phthalate at zero. Based on this goal, the enforceable standard or maximum contaminant level (MCL) is set at six parts per billion (ppb) or 0.006 mg/L. States may set more stringent standards. If DEHP is detected during routine drinking water monitoring, public, regulated utilities take action to reduce the levels below the standards and notify the public within 30 days.
Treating water to remove phthalates to acceptable levels at the tap is easily accomplished. POU treatment using granular activated carbon has been shown to be effective for reduction of phthalates in drinking water. Until the research provides a better assessment of phthalate exposures and health risks, the best precautionary principle is to limit the use of products listing phthalates as an ingredient.
- Centers for Disease Control and Prevention, Phthalates Fact Sheet, CDC, 16 July 2013. [Online]. Available: www.cdc.gov/biomonitoring/phthalates_factsheet.html. [Accessed 17 February 2014].
- Centers for Disease Control and Prevention, Fourth National Report on Human Exposure to Environmental Chemicals, CDC, Atlanta, 2009.
- Sathyanarayana, S., C. J. Karr, P. Lozano, et al., “Baby care products: possible sources of infant phthalate exposure,” Pediatrics, vol. 121, no. 2, pp. e260-268, 2008.
- Ferguson, K. K., T. F. McElrath, J. D. Meeker, “Environmental phthalate exposure and preterm birth,” Journal of the American Medical Association Pediatrics, vol. 168, no. 1, pp. 61-67, 2014.
- US Environmental Protection Agency, Basic Information about di(2-ethylhexyl) Phthalate in Drinking Water, US EPA, 13 December 2013. [Online]. Available: www.epa.gov/drink/contaminants/basicinformation/ di_2-ethylhexyl_phthalate.cfm. [Accessed 17 February 2014].
- National Institutes of Health, Tox Town: Phthalates, NIH, 8 August 2013. [Online]. Available: toxtown.nlm.nih.gov/text_version/chemicals. php?id=24. [Accessed 17 February 2014].
- Koch, H. M., R. Preuss, J. Angerer, “Di(2-ethylhexyl)phthalate (DEHP): human metabolism and internal exposure–an update and latest results,” International Journal of Andrology, vol. 29, no. 1, pp. 155-165, 2006.
About the author
Dr. Kelly A. Reynolds is an Associate Profes- sor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at email@example.com