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Abstract

Healthy People 2020 lists Bisphenol A (BPA) as a potential endocrine disruptor for which exposure should be reduced. The Healthy People 2020 Environmental Health Objectives focus on addressing environmental factors that negatively affect individuals’ health even though the health effects of some toxic substances are not yet fully understood. An American Association of Occupational Health Nurses (AAOHN) position statement outlined the role occupational health nurses play in creating healthy and productive workplaces by promoting worker health. BPA is implicated in a variety of health outcomes such as breast and prostate cancer, menstrual irregularities, genital abnormalities in male babies, infertility in men and women, early puberty in girls, and metabolic disorders such as diabetes and obesity. The overall health issues attributed to BPA exposure are complex and controversial. Concerns regarding environmental health are growing as individuals become more dependent on plastics. Numerous health concerns have been directly connected to daily exposures to products manufactured with BPA. Government agencies support the use of BPA as a safe consumer product with the exception of BPA use in baby bottles and sippy cups, which has been banned in the United States and several other countries. Many agencies (e.g., Federal Drug Administration [FDA], World Health Organization [WHO], U.S. Department of Health & Human Services [U.S. DHHS], and the Centers for Disease Control and Prevention [CDC]) have expressed “some concern” about BPA based on research, and stated further research is warranted.

Keywords

research chronic illnesses disease prevention health promotion occupational hazards

Preserving employee health and safety is a priority for companies and a key function of occupational health nurses. The current American Nurses Association Scope and Standards of Practice 16th Standard states that the practice of registered nurses must be environmentally healthy with an explicit need to incorporate learning activities about environmental health; a specific example provided is health concerns regarding Bisphenol A (BPA; Savell & Sattler, 2012). Nurses play a direct role in promoting employee health including eliminating BPA exposure.

Nurses have a duty to assess and address environmental exposures to promote health and prevent illness by disseminating reliable information to clients and communities (Savell & Sattler, 2012). The Institute of Medicine’s report, Nursing, Health, and the Environment, outlined the need to integrate environmental health into nursing practice; nurses must learn to assess issues in the workplace and advocate for change (Savell & Sattler, 2012).

Healthy People 2020 (2013) lists BPA as a potential endocrine disruptor for which exposure should be reduced. The Healthy People 2020 (2013) Environmental Health Objectives focus on addressing environmental factors that negatively affect individuals’ health even though the health effects of some toxic substances are not yet fully understood.

An American Association of Occupational Health Nurses (AAOHN; 2012) position statement outlined the role occupational health nurses play in creating healthy and productive workplaces by promoting worker health. Chalupka (2010) stated occupational health nurses can provide guidance to employees regarding emerging scientific evidence about the potential health effects of exposure to BPA.

What Is BPA?

BPA is a synthetic compound classified as an endocrine-disrupting chemical that can have severe effects on fetal development after early life exposures (Rogers, Metz, & Yong, 2013). Endocrine-disrupting chemicals

are able to alter the activity of response elements of genes, block natural hormones from binding to their receptors, or in some cases increase the perceived amount of endogenous hormone in the body by acting as a hormone mimic to its receptor. (Rogers et al., 2013, p. 421)

BPA was first produced in 1891, but did not become commonly used until around 1930 when scientists added it to plastic to create polycarbonate plastic. Over eight billion pounds of BPA are produced each year; BPA is one of the most commonly used products in the world, resulting in an estimated one hundred tons released into the atmosphere each year (Rubin, 2011). In 2010, it was reported that BPA grossed around US$6 billion a year for the five U.S. manufacturers of the product (Borrell, 2010). BPA is implicated in a variety of health problems (i.e., breast and prostate cancer, menstrual irregularities, genital abnormalities in male babies, infertility in men and women, early puberty in girls, and metabolic disorders such as diabetes and obesity; Alliance of Nurses for Healthy Environments [ANHE], 2013).

BPA Exposure and Human Disease

Beginning around 1960, manufacturers started adding BPA to many common products (e.g., food and beverage containers, metal food can lining, that is, BPA is used to protectively coat metal cans to prevent contamination and extend product shelf life), plastic eating utensils, toys, eyeglasses, food packaging and reusable containers for food storage, office products, and thermal receipt paper (Vinas, Lopez-Garcia, Campillo, Rivas, & Hernandez-Cordoba, 2012). Once these products go to landfills, BPA is released into the environment, especially surface water (Mazzotta, Malitesta, & Margapoti, 2013). BPA can be ingested or absorbed through skin contact (Birnbaum et al., 2012). To avoid BPA exposure, the following canned foods should be avoided: coconut milk, soup, meat, vegetables, meals (such as ravioli in sauce), juice, fish, beans, meal-replacement drinks, and fruit (Breast Cancer Fund, 2010). Even dental care can expose patients to BPA via epoxy resins.

More than 93% of U.S. adults have detectable levels of urinary BPA (Shankar, Teppala, & Sabanayagam, 2012). Recent animal studies implicate BPA exposure in the development of cardiovascular disease, weight gain, insulin resistance, thyroid dysfunction, endothelial dysfunction, and oxidative stress (Shankar et al., 2012). These researchers analyzed data from 745 participants who completed the National Health and Nutrition Examination Survey 2003-2004 using logistic regression models. Findings support a positive association between increasing levels of urinary BPA and peripheral artery disease independent of pre-existing cardiovascular disease (Shankar et al., 2012).

Although BPA was first approved by the FDA more than 50 years ago, in 2008, the agency raised concerns regarding possible health effects after researchers in the late 1990s and early 2000s conducted animal studies that demonstrated BPA could be a possible cause of diseases. In 2012, the FDA indicated recent studies provided reason for concern, but questioned results from studies that lack consistent research methods and results; no control or unexposed populations are available due to the ubiquity of BPA as is true of animal studies, which have employed a variety of experimental research methods. In 2010, the National Institute of Environmental Health Sciences (NIEHS) directed US$30 million toward BPA research along with US$14 million in stimulus funds to address these issues (Borrell, 2010).

Plastics slowly made their way into the environment without much fanfare. Plastics provide enormous benefits and convenience to individuals, but what price is paid in terms of the health of humans, animals, and the environment? Multiple studies cited by Gentilcore et al. (2013) noted the anti-thyroid effect of BPA exposure, which reduces the expression of the thyroid hormone gene affecting “metabolism, energy provision, development, somatic growth, and reproduction” (p. 22). This effect can be detrimental to the development of fetuses by altering thyroid-specific transcripts in vitro and in vivo (Gentilcore et al., 2013).

In a study by Schug et al. (2012), researchers found a link between BPA exposure and a higher risk of type 2 diabetes, insulin resistance, and increased triglyceride levels and leptin concentrations in pregnant mice and their offspring. Mice exposed to BPA from birth to adulthood showed disruptive estrogen-like responses and alterations in cardiac function, particularly in male mice with increased thickness of the left ventricular wall as well as more cardiac fibrosis and necrosis (Schug et al., 2012).

In a research study supported by the Breast Cancer and the Environment Research Centers, Jenkins, Betancourt, Wang, and Lamartiniere (2012) reported that BPA exposure alters normal estrogen, androgen, and thyroid hormone signaling in vitro. With only 10% to 15% of all breast cancers associated with a hereditary factor, researchers are examining the role of diet, lifestyle, and environmental interactions with chemicals to explain the remaining breast cancer cases. Of particular interest is the timing of exposure to endocrine disruption and the role of endocrine disruption in breast cancer etiology.

Jenkins et al. (2012) reported that BPA contaminates water supplies, dust, air, and even U.S. currency with the primary route of exposure being the leaching of BPA into food from “incomplete polymerization of epoxy resins and polycarbonate plastic or the degradation of the weak ester bonds that link the BPA monomers” (p. 193). Affected products in this report included cardboard milk and juice containers, plastic food wrappers, and other containers exposed to both normal and extreme conditions suggesting widespread exposure to the general population (Jenkins et al., 2012). These authors also published research implicating BPA exposure in “the induction of cell proliferation, producing oxidative stress, and altering cell signaling pathways involved in carcinogenesis and glucose homeostasis” (p. 193). Research by Chalubinski and Kowalski (2006) showed that, along with other endocrine-disrupting chemicals, BPA alters the normal immune response and is implicated in the development of allergies and hay fever by increasing interleukin-4 production and IgE levels.

Using multivariate analysis, an association between BPA exposure during pregnancy and increased risk of infant and early childhood wheezing was reported in a prospective birth cohort study by Spanier et al. (2012). Evidence of wheezing in children at 6 months of age was found, but no evidence of wheezing was found when the children turned 3 years of age (Spanier et al., 2012).

In an occupational cohort study (2004-2008), workers at Chinese epoxy resin manufacturing facilities and corresponding unexposed workers from a variety of other industries without BPA exposure participated in an initial epidemiologic study on parental occupational exposure to BPA during pregnancy (Miao et al., 2011). This research used personal air sampling by exposed workers. A strong association was found between maternal exposure to BPA and fetal reproductive system development (Miao et al., 2011).

In a study of adults on maintenance hemodialysis, plasma BPA levels were elevated and inversely correlated with renal function (Krieter et al., 2013). In this study, both protein-bound and free BPA were analyzed. Adults on maintenance hemodialysis showed 6 times higher BPA concentrations compared with other individuals with chronic kidney disease, but not on dialysis. Because BPA is rapidly eliminated by the kidneys and has a half-life in human blood of less than 2 hours, BPA is normally in the blood at very low levels. In adults with impaired renal function, Krieter et al. (2013) found an accumulation of BPA in the blood, particularly in those individuals exposed to BPA by way of dialyzers contaminated with BPA.

Dermal Exposure to BPA

The U.S. Environmental Protection Agency (EPA; 2012) has stated that contact with “free” discrete, non-polymerized BPA through thermal paper is more common than BPA polymerized in resin or plastic. When individuals handle sales receipts, cinema tickets, labels, ATM receipts, and airline tickets, BPA is transferred to the skin and ingested by hand-to-mouth contact (EPA, 2012). Thermal paper is used extensively in prescription labels, industrial barcodes, packaged items (e.g., supermarket foods found in delis), retail shelf labels, parking tickets, shipping labels, ultrasound and electrocardiogram strips, and printouts from other laboratory recorders (EPA, 2012). Lottery tickets account for 10% of usage and fax paper another 10% (EPA, 2012).

BPA is also found in some cigarette filters; paper currency; luggage tags; flyers, magazines, and newspapers; recycled paper towels, facial tissue, napkins, and toilet paper; printing ink; business cards; and bus, train, and airline tickets. Contact with these products can potentially expose individuals to BPA through dermal contact. Once these products are brought into homes, exposure can also occur through house dust (Liao & Kannan, 2011).

How BPA Affects the Body

BPA is an endocrine-disrupting compound that mimics the action of estrogen causing a decrease in sperm quality in humans and neural and behavioral changes in infants and children as well as other health risks (Mazzotta et al., 2013). The FDA has reported their studies show BPA works exactly opposite from other toxins in the body and is rapidly metabolized and eliminated from the body, posing a negligible health risk even at higher doses (FDA, 2012a). BPA is converted in the gastrointestinal tract and liver to “more water-soluble glucuronide or sulfate conjugates by phase II metabolism” (Teeguarden et al., 2011, p. 49). The half-life of BPA, which is rapidly excreted in urine, ranges from 4 to 43 hours (Trasande, Attina, & Blustein, 2012).

Phase 2 metabolism of BPA and the conversion of BPA to glucuronide conjugate is a critical piece of evidence supporting that BPA does not bind to estrogen receptors (Doerge & Fisher, 2010). Free or unconjugated BPA does not accumulate in the body. Doerge and Fisher (2010) stated that the adult monkey is better suited for studies of BPA glucuronidation because of the high degree of concordance between humans and monkeys versus dogs, bovines, swine, rats, or mice. A strong research recommendation by Doerge and Fisher (2010) is for additional human toxicokinetic studies with high standards of analytical sensitivity and method validation to ensure accurate and precise time-dependent measurements of both conjugated and unconjugated forms of BPA along with complete analysis of urinary excretion.

Research shows BPA is rapidly eliminated from the body after a short single dose exposure, but continuous exposure through diet appears to result in BPA accumulation at detectable levels in serum or plasma (Melzer et al., 2012). These researchers hypothesized the lipophilic nature of BPA causes it to migrate to lipid-rich tissues resulting in slower release. However, without human pharmacokinetic data to support this hypothesis, inferences are made through animal studies (Melzer et al., 2012). Humans come in contact with BPA in a variety of ways; animals are tested in controlled laboratory environments. In humans, BPA is metabolized in the intestines and liver and eliminated via urine, but in rats it is eliminated via bile (Melzer et al., 2012).

Some studies have suggested an association between high levels of BPA and coronary artery disease for individuals who have higher dietary intake suggesting an obesity-related risk rather than strictly an association with BPA (Melzer et al., 2012). In the analysis provided by Melzer et al. (2012), obesity was found to have little effect on this association indicating BPA plays a significant role. These authors suggested several mechanisms for the association between coronary artery disease and BPA exposure: estrogenic, anti-androgenic, and receptor-mediated modes of BPA toxicity (Melzer et al., 2012). The effects of estrogen on cardiovascular tissues is well documented in research. With BPA mimicking estrogen in the body, the supposition is that BPA exerts those same estrogenic effects by binding to soluble or membrane-bound estrogen receptors (Melzer et al., 2012). To conclusively support the association between BPA and the development of coronary artery disease requires long-term and larger human studies, which are constrained by ethical considerations and the practicality of repeated BPA exposure (Melzer et al., 2012).

Products Which Contain BPA

BPA is found in various consumer products that are commonly used in daily life and cash receipts are a few items that may contain high levels of BPA (EPA, 2012). When food is stored in packages made with BPA, heated in a microwave, and exposed to high temperatures, Bisphenol-type compounds can be released from the container contaminating the food being prepared for consumption (Vinas et al., 2012).

BPA is used in the manufacture of epoxy resins that are resistant to heat, chemicals, and electricity, a characteristic of electronic applications. Epoxy resin coating protects pipes and fittings from corrosion. BPA is used in bicycle and motorcycle helmets, safety equipment such as face shields and guards, lifesaving health care devices (e.g., incubators, kidney dialysis machines, and blast- and bullet-resistant shielding). BPA is a key component of epoxy resins used in marine coatings that protect ships’ hulls, offshore drilling platforms, water ballast tanks and cargo linings, coatings on electronic parts, and printed circuit boards, along with a host of other products including industrial flooring and gardening tools (American Chemistry Council [ACC], The Polycarbonate/BPA Global Group, 2009).

Use of BPA in Baby Bottles

BPA was found in the plastic used to manufacture baby bottles. In 2010, Canada became the first country to ban BPA in baby bottles (Rogers et al., 2013). These authors reported on studies showing BPA in amniotic fluid, human neonatal blood, placenta, cord blood, and breast milk, all of which affect the development of reproductive organs (Rogers et al., 2013). Studies presented by Huang, Tan, Wang, and Leung (2012) linked BPA to spontaneous abortion, lower birth weight, and premature birth. Although the researchers stated the mechanism for the link is unknown, BPA has been isolated in human tissue.

In response to a petition filed by the ACC, the Food and Drug Administration (FDA) amended the

food additive regulations to no longer provide for the use of polycarbonate resins in infant feeding bottles (baby bottles) and spill-proof cups, including their closures and lids, designed to help train babies and toddlers to drink from cups (sippy cups). (effective July 17, 2012; Federal Register, 2012, p. 41899)

This regulation simply states the FDA is not basing this regulation on safety concerns, but rather on their research; U.S. manufacturers of polycarbonate resins no longer produce baby bottles and sippy cups with polycarbonate resins and are no longer available in the U.S. market. This regulation is not addressing other products commonly used by infants and toddlers such as pacifiers or teethers, nor does it address labeling of products to indicate they contain BPA.

Environmental Impact of BPA

Not only are products made with BPA of concern, but airborne environmental BPA exposure is also of concern (Fu & Kawamura, 2010). This study found a positive correlation between BPA and 1,3,5-triphenylbenzene, a tracer for burning plastic, which these researchers linked directly to the burning of plastics in domestic waste (Fu & Kawamura, 2010). Another culprit is electronic waste generated by discarded computer-printed circuit boards or spray paints. Data were collected from various locations around the world. This study stated atmospheric BPA was detected in the polar atmosphere, an area once thought to be less affected by pollution. The polar region of the earth exhibits an Arctic haze that is more prominent in the winter than early summer. The study found South Asia had the highest levels of BPA in the atmosphere (Fu & Kawamura, 2010).

How to Minimize BPA Exposure

The FDA provides guidelines to limit BPA exposure by avoiding plastic containers with recycle codes of 3 or 7. Not all containers have a recycle code stamped on the bottom. Caution is needed when ingesting very hot or boiling liquids in these containers or when heating these containers in a microwave (FDA, 2012).

The U.S. DHHS (n.d.) recommended how to minimize infants’ exposures to BPA. First, mothers should breastfeed for the first 12 months whenever possible; if that is not possible, iron-fortified infant formula is the safest and most nutritious alternative. Second, caregivers should discard scratched baby bottles and infant feeding cups because they harbor germs and can release small amounts of BPA. Third, no boiling or very hot water, infant formula, or other liquids should be stored in containers made with BPA; rather boil liquids in a BPA-free container, allow the liquid to cool to lukewarm and then transfer the liquid to another container. For ready-to-feed liquid formula that can be served at room temperature, running warm water over the outside of the bottle should suffice. Never heat baby bottles in the microwave; sterilize and clean bottles according to manufacturer directions and cool to room temperature before adding infant formula. Fourth, always purchase bottles or containers marked “dishwasher safe” before cleaning in a dishwasher.

The U.S. DHHS (n.d.) conceded that small amounts of BPA are found in liquid infant formulas sold in cans and warns not to heat the can on the stove or in boiling water; rather run warm water over the outside of the can. The U.S. DHHS (n.d.) stated the FDA has found no detectable levels of BPA in powdered infant formula. In January 2009, the six major U.S. manufacturers of baby and infant bottles discontinued use of BPA in baby bottles and infant feeding cups. The new brand of BPA-free containers includes Avent, Doctor Brown’s Natural Flow, Evenflow, First Essentials, Gerber, Munchkin, Nuk, and Playtex.

Although several sources referenced in this article indicate some children’s toys are made with plastic that contains BPA, the U.S. DHHS states this belief is generally false and that most toys have BPA added to the plastic. The U.S. DHHS states the part of a pacifier made from latex or silicone that children put in their mouths does not contain BPA, but the hard plastic shield, designed to keep babies from swallowing pacifiers, may contain BPA; however, the exposure is likely negligible. Children are more at risk of BPA harm because their bodies have immature systems for detoxifying chemicals. NIEHS has been provided US$30 million in funding to further investigate BPA.

Government Response to BPA Health Concerns

The FDA’s National Center for Toxicological Research is taking steps to reduce human exposure to BPA in the food supply by supporting the industry’s actions to stop producing BPA-containing baby bottles and infant feeding cups, by facilitating the development of safe alternatives, more oversight of BPA, and seeking public comment regarding BPA (FDA, 2012).

The U.S. EPA (2012) acknowledges BPA is a reproductive, developmental, and systemic toxicant based on animal studies and acknowledges the interaction with estrogen receptors, but questions the potential impact on humans and the environment. In 2010, based on increasing concerns, the EPA released a chemical action plan regarding BPA hazards and exposure information. Based on the EPA’s assessment, most human exposure to BPA comes from food and beverage packaging; less than 5% of the BPA produced is used in food packaging (EPA, 2012).

The EPA has included BPA on the Concern List under the Toxic Substances Control Act (TSCA), but is not initiating regulatory action under TSCA. Under this rule, the EPA, in coordination with the FDA, Centers for Disease Control and Prevention (CDC), and NIEHS is to test or monitor landfills, manufacturing plants, and other similar locations for groundwater and drinking water contamination to determine possible exposures (EPA, 2013). In July 2013, France banned BPA in almost all materials with food contact. Belgium and Switzerland also announced plans to ban BPA in packaging foods intended for children younger than 3 years of age (Sissell, 2012).

Organizations Supporting the Use of BPA

The Polycarbonate/BPA Global Group of the ACC provided their support for BPA as a safe product outlining many uses of this safe consumer product (ACC, The Polycarbonate/BPA Global Group, 2009). Specifically, the ACC documents that the FDA denied the 2012 citizen petition from the Natural Resources Defense Council, which requested the FDA prohibit the use of BPA in human food and food packaging. Also listed are statements from the U.S. DHHS and the FDA that BPA has not been shown to be a health risk for children or adults, but they do note “some concern,” which the FDA will continue to address and monitor (ACC, The Polycarbonate/BPA Global Group, 2009).

Another country’s responses to the ACC’s fact sheet is Health Canada, which states some studies do provide evidence for concern during gestation and early postnatal life; specifically, neural development could be adversely affected by BPA (ACC, The Polycarbonate/BPA Global Group, 2009). The ACC claims support from the European Food Safety Authority and Australia that BPA presents no significant health risks and disputes all claims that BPA causes cancer and heart disease, accumulates in the body, or can be absorbed through the skin (e.g., touching sales receipts; ACC, The Polycarbonate/BPA Global Group, 2009).

The ACC states the benefits of using BPA in manufacturing are durability, shatter-resistance, light weight, and transparency that are required for optical lenses, safety glasses, vehicle windows, and health care equipment. The light weight increases automobile, airplane, and train fuel efficiency; the ACC identifies reducing carbon emissions as an environmental benefit of BPA (ACC, The Polycarbonate/BPA Global Group, 2009). The ACC states another environmental benefit is related to health care equipment that can be repeatedly sterilized reducing health care waste (ACC, The Polycarbonate/BPA Global Group, 2009).

In a statement dated January 25, 2013, the ACC (2013) stated the California Office of Environmental Health Hazard Assessment (OEHHA) assessed the use of BPA, did not find it a risk to human health, and indicated support from the FDA, the World Health Organization (WHO), and other major government agencies around the world.

The FDA states the use of BPA is safe and even if trace amounts do enter the body, it is rapidly metabolized and eliminated without significant health risks (FDA, 2012). In addition, the FDA states their research, as well as European Food Safety Agency research, which show BPA causes multiple health problems have no convincing evidence to support those claims, but the agency will continue to research and monitor BPA effects (FDA, 2012). FDA scientists at the National Center for Toxicological Research are working with the NIEHS and the National Toxicology Program (NTP) to research the toxic health effects of BPA. These researchers estimate the level of infant exposure is from 84% to 92% less than previous studies have indicated (FDA, 2012).

Industry-Sponsored Versus Publicly Sponsored Study Differences

An enormous amount of literature on this topic has been published, both showing little or no adverse effects and significant effects. The Food and Agriculture Organization of the United Nations (FAO) and the WHO came together in November 2010 to assess the safety of BPA. In the executive summary of the Report of Stakeholder Meeting on BPA, their experts contend BPA has low acute toxicity and is a safe product. They question many aspects of existing studies linking BPA to health concerns (WHO, 2010). In particular, this group points out that most epidemiological studies use cross-sectional designs and a single outcome measure (i.e., urinary BPA), which concurrently is used to assess BPA exposure and health outcomes, limiting their interpretability. Cardiovascular disease and diabetes are likely to have a variety of causal mechanisms due to their longer latency periods (WHO, 2010). They also question the use of a single urine sample to categorize exposure because of the short half-life of BPA. The FAO/WHO stakeholder report questioned any direct link between the human immune system and BPA. The report does state further research into metabolic disorders is warranted based on current research (WHO, 2010) The FAO/WHO stakeholder report also stated the exposure to BPA from dental materials was low and did not pose a significant health risk.

In a review article by Hengstler et al. (2011), 5,000 safety-related studies on BPA were reviewed by the Advisory Committee of the German Society of Toxicology. The findings of this review board indicated no noteworthy risk of BPA to the health of the human population. These authors discussed the controversy on BPA safety citing some scientists believe studies funded by chemical corporations result in findings supporting the safety of BPA, whereas the majority of publicly funded studies result in concern about human health. These authors also questioned the consistency of testing methods among studies, specifically exposure methods. Some researchers used subcutaneous injections, whereas others administered BPA orally to animals; how BPA is absorbed and metabolized by the body is significant because non-oral administration bypasses first-pass metabolism and injections may have a slower release of BPA from the oil suspension of the injectables (Hengstler et al., 2011). These authors contend testing methods should be oral because humans come into contact with BPA primarily through oral and dermal routes.

A critical question in the review by Hengstler et al. (2011) is why are rats being used in these studies when they excrete BPA-glucuronide predominantly via bile into the feces resulting in enterohepatic circulation but humans and monkeys excrete BPA-glucuronide predominantly via urine? Hengstler et al. (2011) also stated that no studies have confirmed a direct causal health effect from BPA and at best studies provide hypotheses for an association, especially in regard to diseases that have longer latency periods (e.g., breast cancer).

Analysis of BPA Through Laboratory Studies

Debate continues on how to analyze BPA; how do humans contact BPA and what effects does BPA have on the human body? Cunha, Cunha, Ferreira, and Fernandes (2012) discussed a newer and more reliable procedure for successfully measuring BPA in canned seafood samples. Accurate analysis of seafood requires samples free of fatty compounds, which can alter results. Only glass containers were used in their study to eliminate contamination from plastic tubing. Their study found BPA at levels ranging from 1.0 to 99.9 µg/kg in more than 83% of the 47 products tested, with the current maximum acceptable dose at 50 µg/kg body weight per day according to the 2006 FDA established guidelines (Cunha et al., 2012).

Geens et al. (2012) questioned the feasibility of human epidemiological studies because BPA cannot be isolated from the mixture of endocrine-disrupting chemicals to which humans are exposed and no “control” or unexposed population exists due to the ubiquity of BPA. Geens et al. (2012) reviewed literature from 2009 to 2011 and reported the highest urinary concentrations of BPA in adolescents ages 12 to 19 years, followed by children ages 6 to 11 years, and then adults older than 19 years.

In a non-randomized intervention of 77 Harvard College students, Carwile et al. (2009) found an association between increased urinary BPA concentrations and students who regularly consumed cold beverages stored in polycarbonate bottles. The study consisted of a 1-week washout phase where the participants only drank cold beverages from stainless steel bottles compared with 1-week of regularly consuming cold beverages in polycarbonate containers. The washout phase showed urinary BPA levels at 1.2 µg/g creatinine and increased to 2.0 µg/g creatinine after 1-week of polycarbonate bottle use (Carwile et al., 2009). Other possible sources of BPA exposure were not controlled in this study (Carwile et al., 2009).

Study Analysis

“The majority of epidemiological studies used cross-sectional designs with a single measurement of urinary BPA. Cross-sectional studies have limited interpretability, especially for outcomes that have a long latency period (e.g., cardiovascular disease, diabetes)” (Geens et al., 2012, p. 3736). Epidemiological studies are difficult to interpret for the following reasons (Geens et al., 2012):

○ Humans are exposed to numerous and varied endocrine disruptors, thus, it is difficult to identify specific effects of BPA; BPA has the ability to interact with human estrogen receptors of a, b, and c subtypes, and in vitro experiments have revealed significant estrogen and androgen activity of BPA. In addition, thyroid hormone receptors, PPAR-gamma receptors and GPR30 receptors could be involved.

○ Endocrine disrupters’ impact on sexual development, reproduction potency, and health (i.e., especially cancers of sexual organs but also cardiovascular diseases and diabetes) depends on exposure time (e.g., in utero, newborn babies, adolescents, adults, menopausal women). Early exposure is more likely to account for effects due to the vulnerability of homeostatic processes (e.g., control of reproduction and energy balance). (p. 3736)

Concerns Regarding Experimental Design, Analysis, and Reporting Criteria

In endocrinology experiments with laboratory animals, Richter et al. (2007) outlined data that must be provided by researchers when they report their study findings:

The animal model and supplier being used should be published because the outcomes may be confounded by these variables.

Listed concerns are hormonally active components of feed, water, or caging; species and strains differ in their sensitivity to hormone-active compounds.

Example: Sprague-Dawley rats from different commercial breeders are an outbred stock and therefore are not the same.

Sprague-Dawley CD rats from Charles River Laboratories have very low sensitivity to exogenous estrogens. Also, they are bred for a large body size and litter size so they must be identified separately.

CD (SD) rats, both male and female, are highly sensitive to exposure of low doses of BPA during development.

Feed must be identified as soy-based and non-soy-based related to estrogenic components. The same mill date of the feed should be used throughout the experiment.

The type of cage should be BPA-free and water bottles should not be used because these bottles can leach BPA to the animals.

The precise method of dosing and the time of dosing must be identified due to first-pass metabolism of BPA in the liver with oral exposure.

The litter must be accounted for as this is a significant source of variation.

The timing of exposure to endocrine disruptors can have varying effects depending on the life stage of the animal.

Birnbaum et al. (2012) outlined concerns raised by the NIEHS and the FDA regarding critical data gaps in research. The resulting document is referred to as the Chapel Hill Consensus Statement.

Key sources of uncertainty that have been identified include

Absent or inconsistent data on dose response, including low-dose effects and nonmonotonic dose-response behaviors;

Pharmacokinetics across species and life-span;

Differences between the sexes;

Routes and extent of human exposures;

Sensitive windows of exposure;

Mechanism(s);

Specific disease end points; and

Difficulty in extrapolating data from animals to humans and comparing results from studies compliant with acceptable laboratory practices and those initiated by academic investigators (Birnbaum et al., 2012, p. 1641)

Additional Resources

The University of Massachusetts at Lowell online database includes state and local legislative and executive branch policies from all 50 states (1990 to present) that regulate or ban specific chemicals and provide comprehensive state policy reforms, biomonitoring programs, and safer chemical alternatives. http://www.chemicalspolicy.org/chemicalspolicy.us.state.database.php

The Washington Department of Ecology created the Reducing Toxic Threats initiative http://www.ecy.wa.gov/toxics/index.htm

EPA Action Plan summary http://www.epa.gov/oppt/existingchemicals/pubs/actionplans/bpa.html

Consumer Product Safety Commission (CPSC) http://www.cpsc.gov/

U.S. Food and Drug Administration (FDA)http://www.fda.gov/

National Institute for Occupational Safety and Health (NIOSH; part of the Centers for Disease Control and Prevention [CDC]) http://www.cdc.gov/niosh/

The National Institute of Environmental Health Sciences http://www.niehs.nih.gov/

U.S. Department of Health and Human Services (DHHS) http://www.hhs.gov

Bisphenol A. (CASRN [Chemical Abstract Services Registry Number] 80-05-7)

Synonyms

Substance Name—Bisphenol A.

CASRN—80-05-7

Last Revised—09/26/1988

80-05-7

bisferol A

Bisphenol A.

2,2-bis-4’-hydroxyfenylpropan

bis(4-hydroxyphenyl) dimethylmethane

2,2-bis(4-hydroxyphenyl)propane

2,2-bis(p-hydroxyphenyl)propane

bis(4-hydroxyphenyl)propane

bisphenol

bisphenol A

Bisphenol A.

4,4’-bisphenol A

dian

4,4’-dihydroxydiphenyldimethylmethane

p,p’-dihydroxydiphenyldimethylmethane

2,2-(4,4’-dihydroxydiphenyl)propane

4,4’-dihydroxydiphenylpropane

4,4’-dihydroxydiphenyl-2,2-propane

p,p’-dihydroxydiphenylpropane

2,2-di(4-hydroxyphenyl)propane

beta-di-p-hydroxyphenylpropane

dimethyl bis(p-hydroxyphenyl)methane

dimethylmethylene-p,p’-diphenol

diphenylolpropane

2,2-di(4-phenylol)propane

4,4’-isopropylidenebisphenol

p,p’-isopropylidenebisphenol

p,p’-isopropylidenediphenol

NCI-C50635

phenol, 4,4’-dimethylmethylenedi-

phenol, 4,4’-isopropylidenedi-

propane, 2,2-bis(p-hydroxyphenyl)-

http://www.epa.gov/iris/subst/0356.htm

Standard 16. Environmental Health

The registered nurse practices in an environmentally safe and healthy manner.

Competencies

The registered nurse:

Attains knowledge of environmental health concepts, such as implementation of environmental health strategies.

Promotes a practice environment that reduces environmental health risks for workers and healthcare consumers.

Assesses the practice environment for factors such as sound, odor, noise, and light that threaten health.

Advocates for the judicious and appropriate use of products in health care.

Communicates environmental health risks and exposure reduction strategies to healthcare consumers, families, colleagues, and communities.

Utilizes scientific evidence to determine if a product or treatment is an environmental threat.

Participates in strategies to promote healthy communities.

Footnotes

Conflict of Interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Author Biography

Cynthia Marie Metz, MS, BSN, RN, is currently employed at Texas Instruments as an occupational health nurse consultant.

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