At TEDX we publish scientific reviews, commentaries, and original research. Many of our publications are conducted in collaboration with other scientists. We use our expertise to answer important research questions and support informed decision making. Our work is used by government and non-government organizations to protect health by reducing harmful chemicals in our indoor and outdoor environments, and the womb.
Environmental chemicals and autism: a scoping review of the human and animal research
Pelch KE, Bolden AL, Kwiatkowski CF. 2019. Environmental Health Perspectives 127(4). doi:10.1289/EHP4386.
Estimates of autism prevalence have increased dramatically over the past two decades. Evidence suggests environmental factors may contribute to the etiology of the disorder.
This scoping review aimed to identify and categorize primary research and reviews on the association between prenatal and early postnatal exposure to environmental chemicals and the development of autism in epidemiological studies and rodent models of autism.
PubMed was searched through 8 February 2018. Included studies assessed exposure to environmental chemicals prior to 2 months of age in humans or 14 d in rodents. Rodent studies were considered relevant if they included at least one measurement of reciprocal social communicative behavior or repetitive and stereotyped behavior. Study details are presented in interactive displays using Tableau Public.
The search returned 21,603 unique studies, of which 54 epidemiological studies, 46 experimental rodent studies, and 50 reviews were deemed relevant, covering 152 chemical exposures. The most frequently studied exposures in humans were particulate matter (n=14), mercury (n=14), nonspecific air pollution (n=10), and lead (n=10). In rodent studies, the most frequently studied exposures were chlorpyrifos (n=9), mercury (n=6), and lead (n=4).
Although research is growing rapidly, wide variability exists in study design and conduct, exposures investigated, and outcomes assessed. Conclusions focus on recommendations to guide development of best practices in epidemiology and toxicology, including greater harmonization across these fields of research to more quickly and efficiently identify chemicals of concern. In particular, we recommend chlorpyrifos, lead, and polychlorinated biphenyls (PCBs) be systematically reviewed in order to assess their relationship with the development of autism. There is a pressing need to move forward quickly and efficiently to understand environmental influences on autism in order to answer current regulatory questions and inform treatment and prevention efforts. https://doi.org/10.1289/EHP4386
Protocol for a systematic map of the evidence of migrating and extractable chemicals from food contact articles
Martin OV, Geueke B, Groh KJ, Chevrier J, Fini JB, Houlihan J, Kassotis C, Myers P, Nagel SC, Pelch KE, Sargis RM, Trasande L, Vandenberg LN, Wagner M, Maffini MV, Muncke J. 2018. Zenodo. 2018, December 23. doi:10.5281/zenodo.2525277..
Final protocol uploaded to Zenodo and attributed the following digital object identifier (DOI) 10.5281/zenodo.2525277.
Approximately 10,000 substances are intentionally used in the manufacture of food contact materials (FCMs), and an estimated 40,000 to 100,000 substances are thought to be present in all different types of food contact articles (FCAs) (Grob et al. 2006). FCMs and FCAs come into direct contact with foodstuffs; their chemical constituents, food contact chemicals (FCCs), can be transferred into food by the process of chemical migration (Arvanitoyannis and Bosnea 2004). Since almost all foodstuffs come into contact with FCAs during their production, storage, processing
and/or packaging, there is most likely wide exposure of the human population to FCCs (Muncke et al. 2014). However, the extent of this exposure, and the variability of exposure between individuals and populations, is essentially unknown. Further, the human health effects related to chronic, low-level chemical exposures via food are poorly understood, and the available scientific evidence mostly
focuses on a few very well studied FCCs which are known chemicals of concern such as bisphenol A, ortho-phthalates, and perfluorooctanoic acid (Muncke et al. 2017; Trasande et al. 2018).
More research is needed to better understand the relationships between FCC exposures and human health effects. As a first step, completion of this protocol will allow us to compile the available scientific evidence about chemical migration from and/or extractable from FCAs. Follow-up studies not described in this protocol, but based on the outcome of this work, will address human exposure to FCCs, as well as the human health outcomes implicated with human exposure to FCCs, in order to
characterize the state-of-the-science and identify key knowledge gaps. The focus of this work is on indirect food additives and it excludes all chemicals intentionally added to food (e.g. food additives) or unintentionally added to food through a process unrelated to FCA (e.g. pesticides, herbicides, etc).
Exploring the endocrine activity of air pollutants associated with unconventional oil and gas extraction
Bolden AL, Schultz K, Pelch KE, Kwiatkowski CF. 2018. Environmental Health 17:26. doi:10.1186/s12940-018-0368-z.
Background: In the last decade unconventional oil and gas (UOG) extraction has rapidly proliferated throughout the United States (US) and the world. This occurred largely because of the development of directional drilling and hydraulic fracturing which allows access to fossil fuels from geologic formations that were previously not cost effective to pursue. This process is known to use greater than 1,000 chemicals such as solvents, surfactants, detergents, and biocides. In addition, a complex mixture of chemicals, including heavy metals, naturally-occurring radioactive chemicals, and organic compounds are released from the formations and can enter air and water. Compounds associated with UOG activity have been linked to adverse reproductive and developmental outcomes in humans and laboratory animal models, which is possibly due to the presence of endocrine active chemicals.
Methods: Using systematic methods, electronic searches of PubMed and Web of Science were conducted to identify studies that measured chemicals in air near sites of UOG activity. Records were screened by title and abstract, relevant articles then underwent full text review, and data were extracted from the studies. A list of
chemicals detected near UOG sites was generated. Then, the potential endocrine activity of the most frequently detected chemicals was explored via searches of literature from PubMed.
Results: Evaluation of 48 studies that sampled air near sites of UOG activity identified 106 chemicals detected in two or more studies. Ethane, benzene and n-pentane were the top three most frequently detected. Twenty-one chemicals have been shown to have endocrine activity including estrogenic and androgenic activity and the ability to alter steroidogenesis. Literature also suggested that some of the air pollutants may affect reproduction, development, and neurophysiological function, all endpoints which can be modulated by hormones. These chemicals included aromatics (i.e., benzene, toluene, ethylbenzene, and xylene), several polycyclic aromatic hydrocarbons, and mercury.
Conclusion: These results provide a basis for prioritizing future primary studies regarding the endocrine disrupting properties of UOG air pollutants, including exposure research in wildlife and humans. Further, we recommend systematic reviews of the health impacts of exposure to specific chemicals, and comprehensive environmental sampling of a broader array of chemicals.
Prenatal exposure to bisphenol A and hyperactivity in children: a systematic review and meta-analysis
Rochester JR, Bolden AB, Kwiatkowski CF. 2018. Environment International 2018; doi:10.1016/j.envint.2017.12.028.
Background: Attention-deficit hyperactivity disorder (ADHD) has increased in prevalence in the past decade. Studies attempting to identify a specific genetic component have not been able to account for much of the heritability of ADHD, indicating there may be gene-environment interactions underlying the disorder, including early exposure to environmental chemicals. Based on several relevant studies, we chose to examine bisphenol A (BPA) as a possible contributor to ADHD in humans. BPA is a widespread environmental chemical that has been shown to disrupt neurodevelopment in rodents and humans.
Objectives: Using the Office of Health Assessment and Translation (OHAT) framework, a systematic review and meta-analysis was designed to determine the relationship between early life exposure to BPA and hyperactivity, a key diagnostic criterion of ADHD.
Data sources: Searches of PubMed, Web of Science, and Toxline were completed for all literature to January 1, 2017.
Study eligibility criteria: For inclusion, the studies had to publish original data, be in the English language, include a measure of BPA exposure, and assess if BPA exposure affected hyperactive behaviors in mice, rats or humans. Exposure to BPA had to occur at <3 months of age for humans, up to postnatal day 35 for rats and up to postnatal day 40 for mice. Exposure could occur either gestationally (via maternal exposure) or directly to the offspring.
Study appraisal and synthesis methods: Studies were evaluated using the OHAT risk of bias tool. The effects in humans were assessed qualitatively. For rodents exposed to 20 μg/kg/day BPA, we evaluated the study findings in a random effects meta-analytical model.
Results: A review of the literature identified 29 rodent and 3 human studies. A random effects meta-analysis showed significantly increased hyperactivity in male rodents. In humans, early BPA exposure was associated with hyperactivity in boys and girls.
Limitations, conclusions, and implications of key findings: We concluded that early life BPA exposure is a presumed human hazard for the development of hyperactivity. Possible limitations of this systematic review include deficiencies in author reporting, exclusion of some literature based on language, and insufficient similarity between human studies. SRs that result in hazard-based conclusions are the first step in assessing and mitigating risks. Given the widespread exposure of BPA and increasing diagnoses of ADHD, we recommend immediate actions to complete such risk analyses and take next steps for the protection of human health. In the meantime, precautionary measures should be taken to reduce exposure in pregnant women, infants and children. The present analysis also discusses potential mechanisms by which BPA affects hyperactivity, and the most effective avenues for future research.
Is it time to reassess current safety standards for glyphosate-based herbicides?
Vandenberg LN, Blumberg B, Antoniou MN, Benbrook CM, Carroll L, Colborn T, Everett LG, Hansen M, Landrigan PJ, Lanphear BP, Mesnage R, Vom Saal FS, Welshons WV, Myers JP. 2017. J Epidemiol Community Health 71(6):613-618. doi:10.1136/jech-2016-208463.
Use of glyphosate-based herbicides (GBHs) increased ∼100-fold from 1974 to 2014. Additional increases are expected due to widespread emergence of glyphosate-resistant weeds, increased application of GBHs, and preharvest uses of GBHs as desiccants. Current safety assessments rely heavily on studies conducted over 30 years ago. We have considered information on GBH use, exposures, mechanisms of action, toxicity and epidemiology. Human exposures to glyphosate are rising, and a number of in vitro and in vivo studies challenge the basis for the current safety assessment of glyphosate and GBHs. We conclude that current safety standards for GBHs are outdated and may fail to protect public health or the environment. To improve safety standards, the following are urgently needed: (1) human biomonitoring for glyphosate and its metabolites; (2) prioritisation of glyphosate and GBHs for hazard assessments, including toxicological studies that use state-of-the-art approaches; (3) epidemiological studies, especially of occupationally exposed agricultural workers, pregnant women and their children and (4) evaluations of GBHs in commercially used formulations, recognising that herbicide mixtures likely have effects that are not predicted by studying glyphosate alone.
Potential developmental and reproductive impacts of triclocarban: A scoping review
Rochester JR, Bolden AL, Pelch KE, Kwiatkowski CF. 2017. Journal of Toxicology 2017:15 pages; doi:10.1155/2017/9679738.
Triclocarban (TCC) is an antimicrobial agent used in personal care products. Although frequently studied with another antimicrobial, triclosan, it is not as well researched, and there are very few reviews of the biological activity of TCC. TCC has been shown to be a possible endocrine disruptor, acting by enhancing the activity of endogenous hormones. TCC has been banned in the US for certain applications; however, many human populations, in and outside the US, exhibit exposure to TCC. Because of the concern of the health effects of TCC, we conducted a scoping review in order to map the current body of literature on the endocrine, reproductive, and developmental effects of TCC. The aim of this scoping review was to identify possible endpoints for future systematic review and to make recommendations for future research. A search of the literature until August 2017 yielded 32 relevant studies in humans, rodents, fish, invertebrates, and in vitro. Based on the robustness of the literature in all three evidence streams (human, animal, and in vitro), we identified three endpoints for possible systematic review: estrogenic activity, androgenic activity, and offspring growth. In this review, we describe the body of evidence and make recommendations for future research.
Melamine, beyond the kidney: A ubiquitous endocrine disruptor and neurotoxicant?
Bolden AL, Rochester JR, Kwiatkowski CF. 2017. Toxicol Lett 280:181-189; doi:10.1016/j.toxlet.2017.07.893.
Melamine is commonly used in a variety of consumer products such as furniture, dining ware, and food utensils. The chemical infamously gained worldwide attention by its illegal addition to a variety of foodstuffs in order to falsify protein content, which led to serious, sometimes fatal, health impacts in children and pets. This resulted in a large amount of published primary studies and reviews of the impacts of melamine exposure on kidney function. However, a growing body of literature suggests that melamine may have impacts beyond renal dysfunction. We conducted a scoping review of this literature which yielded more than 40 studies with human, animal, and in vitro findings. Neurological impacts, reproductive function, and anthropometric outcomes were identified as possible candidates for systematic review based on evidence stream and replication of endpoints. The results of this analysis provide a basis for prioritizing future research on health impacts associated with melamine exposure.
Polycyclic aromatic hydrocarbons and female reproductive health: A scoping review
Bolden AL, Rochester JR, Schultz K, Kwiatkowski CF. 2017. Reprod Toxicol 73:61-74. doi: 10.1016/j.reprotox.2017.07.012.
Polycyclic aromatic hydrocarbons (PAHs) are a class of common persistent environmental pollutants found in water, air, soil, and plants and can be released by natural sources. However, the majority of atmospheric PAHs are from vehicular emissions, coal-burning plants, and the production and use of petroleum-derived substances. Exposure to PAHs has been implicated in cancer and other diseases, including reproductive disorders. This scoping review is a preliminary step that explores the utility and feasibility of completing a systematic review evaluating the effect of PAHs on female reproduction. We performed literature searches in PubMed, Web of Science, and Scopus, then screened, identified, and categorized relevant studies. Our results identified fertility and pregnancy/fetal viability as outcomes with sufficient research for systematic review. In addition to presenting the relevant studies, the review identifies data gaps, and provides the groundwork to develop the most appropriate research questions for systematic review.
The Age of Chemicals in the 21st Century: New Inventions, New Problems
Kwiatkowski, CF. 2017. Weil Integrative Medicine Library.
Dr. Kwiatkowski wrote the introductory chapter to the book Integrative Environmental Medicine, edited by Aly Cohen and Frederick vom Saal. The book shares the full story of environmental medicine, from the history of plastics and chemicals, to regulatory failures, to the health consequences of water and air contamination and the rising incidence of disease in the U.S. It also offers tangible, practical information that can easily be integrated into the daily work flow of patient clinical care; websites, phone apps, physician and patient handouts and printable lists.
Twenty-Five Years of Endocrine Disruption Science: Remembering Theo Colborn
Kwiatkowski CF, Bolden AL, Liroff RA, Rochester JR, Vandenbergh JG. 2016. Environ Health Perspect 124:A151–A154; doi:10.1289/EHP746.
For nearly 30 years, Dr. Theo Colborn (1927–2014) dedicated herself to studying the harmful effects of endocrine-disrupting chemicals on wildlife, humans, and the environment. More recently, she extended this effort to address the health impacts of unconventional oil and gas development. Colborn was a visionary leader who excelled at synthesizing scientific findings across disciplines. Using her unique insights and strong moral convictions, she changed the face of toxicological research, influenced chemical regulatory policy, and educated the public. In 2003, Colborn started a nonprofit organization—The Endocrine Disruption Exchange (TEDX). As we celebrate the 25th anniversary of endocrine disruption science, TEDX continues her legacy of analyzing the extensive body of environmental health research and developing unique educational resources to support public policy and education. Among other tools, TEDX currently uses the systematic review framework developed by the National Toxicology Program at the National Institute of Environmental Health Sciences, to answer research questions of pressing concern. In this article, we pay homage to the tenacious woman and the exemplary contribution she made to the field of environmental health. Recommendations for the future of the field are drawn from her wisdom.
Minireview: Endocrine Disruptors: Past Lessons and Future Directions
Schug TT, Johnson AF, Birnbaum LS, Colborn T, Guillette LJ, Crews DP, Collins T, Soto AM, vom Saal FS, McLachlan JA, Sonnenschein C, Heindel JJ. 2016. Mol Endocrinol 30(8):833-847; doi:10.1210/me.2016-1096.
Within the past few decades, the concept of endocrine-disrupting chemicals (EDCs) has risen from a position of total obscurity to become a focus of dialogue, debate, and concern among scientists, physicians, regulators, and the public. The emergence and development of this field of study has not always followed a smooth path, and researchers continue to wrestle with questions about the low-dose effects and nonmonotonic dose responses seen with EDCs, their biological mechanisms of action, the true pervasiveness of these chemicals in our environment and in our bodies, and the extent of their effects on human and wildlife health. This review chronicles the development of the unique, multidisciplinary field of endocrine disruption, highlighting what we have learned about the threat of EDCs and lessons that could be relevant to other fields. It also offers perspectives on the future of the field and opportunities to better protect human health.
Project TENDR: Targeting Environmental Neuro-Developmental Risks. The TENDR Consensus Statement
Bennett D, Bellinger DC, Birnbaum LS, Bradman A, Chen A, Cory-Slechta DA, Engel SM, Fallin MD, Halladay A, Hauser R, Hertz-Picciotto I, Kwiatkowski CF, Lanphear BP, Marquez E, Marty M, McPartland J, Newschaffer CJ, Payne-Sturges D, Patisaul HB, Perera FP, Ritz B, Sass J, Schantz SL, Webster TF, Whyatt RM, Woodruff TJ, Zoeller RT, Anderko L, Campbell C, Conry JA, DeNicola N, Gould RM, Hirtz D, Huffling K, Landrigan PJ, Lavin A, Miller M, Mitchell MA, Rubin L, Schettler T, Tran HL, Acosta A, Brody C, Miller E, Miller P, Swanson M, Witherspoon NO. 2016. Environ Health Perspect 124:A118–A122; doi:10.1289/EHP358.
Summary: Children in America today are at an unacceptably high risk of developing neurodevelopmental disorders that affect the brain and nervous system including autism, attention deficit hyperactivity disorder, intellectual disabilities, and other learning and behavioral disabilities. These are complex disorders with multiple causes—genetic, social, and environmental. The contribution of toxic chemicals to these disorders can be prevented.
Approach: Leading scientific and medical experts, along with children’s health advocates, came together in 2015 under the auspices of Project TENDR: Targeting Environmental Neuro-Developmental Risks to issue a call to action to reduce widespread exposures to chemicals that interfere with fetal and children’s brain development. Based on the available scientific evidence, the TENDR authors have identified prime examples of toxic chemicals and pollutants that increase children’s risks for neurodevelopmental disorders. These include chemicals that are used extensively in consumer products and that have become widespread in the environment. Some are chemicals to which children and pregnant women are regularly exposed, and they are detected in the bodies of virtually all Americans in national surveys conducted by the U.S. Centers for Disease Control and Prevention. The vast majority of chemicals in industrial and consumer products undergo almost no testing for developmental neurotoxicity or other health effects.
Conclusion: Based on these findings, we assert that the current system in the United States for evaluating scientific evidence and making health-based decisions about environmental chemicals is fundamentally broken. To help reduce the unacceptably high prevalence of neurodevelopmental disorders in our children, we must eliminate or significantly reduce exposures to chemicals that contribute to these conditions. We must adopt a new framework for assessing chemicals that have the potential to disrupt brain development and prevent the use of those that may pose a risk. This consensus statement lays the foundation for developing recommendations to monitor, assess, and reduce exposures to neurotoxic chemicals. These measures are urgently needed if we are to protect healthy brain development so that current and future generations can reach their fullest potential.
Concerns Over Use of Glyphosate-based Herbicides and Risks Associated with Exposures: A Consensus Statement
Myers JP, Antoniou MN, Blumberg B, Carroll L, Colborn T, Everett LG, Hansen M, Landrigan PJ, Lanphear BP, Mesnage R, et al. 2016. Environmental Health 15(1):1-13; doi:10.1186/s12940-016-0117-0.
The broad-spectrum herbicide glyphosate (common trade name “Roundup”) was first sold to farmers in 1974. Since the late 1970s, the volume of glyphosate-based herbicides (GBHs) applied has increased approximately 100-fold. Further increases in the volume applied are likely due to more and higher rates of application in response to the widespread emergence of glyphosate-resistant weeds and new, pre-harvest, dessicant use patterns. GBHs were developed to replace or reduce reliance on herbicides causing well-documented problems associated with drift and crop damage, slipping efficacy, and human health risks. Initial industry toxicity testing suggested that GBHs posed relatively low risks to non-target species, including mammals, leading regulatory authorities worldwide to set high acceptable exposure limits. To accommodate changes in GBH use patterns associated with genetically engineered, herbicide-tolerant crops, regulators have dramatically increased tolerance levels in maize, oilseed (soybeans and canola), and alfalfa crops and related livestock feeds. Animal and epidemiology studies published in the last decade, however, point to the need for a fresh look at glyphosate toxicity. Furthermore, the World Health Organization’s International Agency for Research on Cancer recently concluded that glyphosate is “probably carcinogenic to humans.” In response to changing GBH use patterns and advances in scientific understanding of their potential hazards, we have produced a Statement of Concern drawing on emerging science relevant to the safety of GBHs. Our Statement of Concern considers current published literature describing GBH uses, mechanisms of action, toxicity in laboratory animals, and epidemiological studies. It also examines the derivation of current human safety standards. We conclude that: (1) GBHs are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science. We offer a series of recommendations related to the need for new investments in epidemiological studies, biomonitoring, and toxicology studies that draw on the principles of endocrinology to determine whether the effects of GBHs are due to endocrine disrupting activities. We suggest that common commercial formulations of GBHs should be prioritized for inclusion in government-led toxicology testing programs such as the U.S. National Toxicology Program, as well as for biomonitoring as conducted by the U.S. Centers for Disease Control and Prevention.
New Look at BTEX: Are Ambient Levels a Problem?
Bolden AL, Kwiatkowski C, Colborn T. 2015. Environmental Science and Technology doi:10.1021/es505316f.
Benzene, toluene, ethylbenzene, and xylene (BTEX) are retrieved during fossil fuel extraction and used as solvents in consumer and industrial products, as gasoline additives, and as intermediates in the synthesis of organic compounds for many consumer products. Emissions from the combustion of gasoline and diesel fuels are the largest contributors to atmospheric BTEX concentrations. However, levels indoors (where people spend greater than 83% of their time) can be many times greater than outdoors. In this review we identified epidemiological studies assessing the noncancer health impacts of ambient level BTEX exposure (i.e., nonoccupational) and discussed how the health conditions may be hormonally mediated. Health effects significantly associated with ambient level exposure included sperm abnormalities, reduced fetal growth, cardiovascular disease, respiratory dysfunction, asthma, sensitization to common antigens, and more. Several hormones including estrogens, androgens, glucocorticoids, insulin, and serotonin may be involved in these health outcomes. This analysis suggests that all four chemicals may have endocrine disrupting properties at exposure levels below reference concentrations (i.e., safe levels) issued by the U.S. Environmental Protection Agency. These data should be considered when evaluating the use of BTEX in consumer and industrial products and indicates a need to change how chemicals present at low concentrations are assessed and regulated.
Bisphenol S and F: A Systematic Review and Comparison of the Hormonal Activity of Bisphenol A Substitutes
Rochester JR, Bolden AL. 2015. Environmental Health Perspectives doi: 10.1289/ehp.1408989.
Background: Increasing concern over bisphenol A (BPA) as an endocrine-disrupting chemical and its possible effects on human health have prompted the removal of BPA from consumer products, often labeled “BPA-free.” Some of the chemical replacements, however, are also bisphenols and may have similar physiological effects in organisms. Bisphenol S (BPS) and bisphenol F (BPF) are two such BPA substitutes.
Objectives: This review was carried out to evaluate the physiological effects and endocrine activities of the BPA substitutes BPS and BPF. Further, we compared the hormonal potency of BPS and BPF to that of BPA.
Methods: We conducted a systematic review based on the Office of Health Assessment and Translation (OHAT) protocol.
Results: We identified the body of literature to date, consisting of 32 studies (25 in vitro only, and 7 in vivo). The majority of these studies examined the hormonal activities of BPS and BPF and found their potency to be in the same order of magnitude and of similar action as BPA (estrogenic, antiestrogenic, androgenic, and antiandrogenic) in vitro and in vivo. BPS also has potencies similar to that of estradiol in membrane-mediated pathways, which are important for cellular actions such as proliferation, differentiation, and death. BPS and BPF also showed other effects in vitro and in vivo, such as altered organ weights, reproductive end points, and enzyme expression.
Conclusions: Based on the current literature, BPS and BPF are as hormonally active as BPA, and they have endocrine-disrupting effects.
Bisphenol A and Human Health: A Review of the Literature
Rochester JR. 2013. Reproductive Toxicology 42C:132-155; doi:10.1016/j.reprotox.2013.08.008.
There is growing evidence that bisphenol A (BPA) may adversely affect humans. BPA is an endocrine disruptor that has been shown to be harmful in laboratory animal studies. Until recently, there were relatively few epidemiological studies examining the relationship between BPA and health effects in humans. However, in the last year, the number of these studies has more than doubled. A comprehensive literature search found 91 studies linking BPA to human health; 53 published within the last year. This review outlines this body of literature, showing associations between BPA exposure and adverse perinatal, childhood, and adult health outcomes, including reproductive and developmental effects, metabolic disease, and other health effects. These studies encompass both prenatal and postnatal exposures, and include several study designs and population types. While it is difficult to make causal links with epidemiological studies, the growing human literature correlating environmental BPA exposure to adverse effects in humans, along with laboratory studies in many species including primates, provides increasing support that environmental BPA exposure can be harmful to humans, especially in regards to behavioral and other effects in children.
Regulatory Decisions on Endocrine Disrupting Chemicals Should Be Based on the Principles of Endocrinology
Vandenberg LN, Colborn T, Hayes TB, Heindel JJ, Jacobs DR Jr, Lee DH, Shioda T, Sota AM, Vom Saal FS, Welshons WV, Zoeller RT. 2013. Reproductive Toxicology 38:1-15; doi:10.1016/j.reprotox.2013.02.002.
For years, scientists from various disciplines have studied the effects of endocrine disrupting chemicals (EDCs) on the health and wellbeing of humans and wildlife. Some studies have specifically focused on the effects of low doses, i.e. those in the range that are thought to be safe for humans and/or animals. Others have focused on the existence of non-monotonic dose-response curves. These concepts challenge the way that chemical risk assessment is performed for EDCs. Continued discussions have clarified exactly what controversies and challenges remain. We address several of these issues, including why the study and regulation of EDCs should incorporate endocrine principles; what level of consensus there is for low dose effects; challenges to our understanding of non-monotonicity; and whether EDCs have been demonstrated to produce adverse effects. This discussion should result in a better understanding of these issues, and allow for additional dialog on their impact on risk assessment.
Hormones and Endocrine-disrupting Chemicals: Low-dose Effects and Nonmonotonic Dose Responses
Vandenberg LN, Colborn T, Hayes TB, Heindel JJ, Jacobs DR Jr, Lee DH, Shioda T, Soto AM, Vom Saal FS, Welshons WV, Zoeller RT, Myers JP. 2012. Endocrine Reviews 33(3):378-455; doi:10.1210/er.2011-1050.
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, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.
Re: Good Laboratory Practices and Safety Assessments. [Response to Becker et al., Environmental Health Perspectives 117(11):A482-483]
Myers JP, vom Saal FS, Akingbemi BT, Arizono K, Belcher S, Colborn T, Chahoud I, Crain DA , Farabollini F, Guillette LJ Jr, Hassold T, Ho SM, Hunt PA, Iguchi T, Jobling S, Kanno J, Laufer H, Marcus M, McLachlan JA, Nadal A, Oehlmann J, Olea N, Palanza P, Parmigiani S, Rubin BS, Schoenfelder G, Sonnenschein C, Soto AM, Talsness CE, Taylor JA, Vandenberg LN, Vandenbergh JG, Vogel S, Watson CS, Welshons WV, Zoeller RT. 2009. Environmental Health Perspectives 117(11):A483-484; doi:10.1289/ehp.0900884R.
We are in complete agreement with the statement by Becker et al. that “having confidence in scientific procedures and data is the sine qua non for determining the safety of chemicals and chemical products.” Our aim in writing the commentary (Myers et al. 2009) was not to challenge the original intent of Good Laboratory Practices (GLP) requirements, which was to establish standards of record keeping in contract laboratory research so as to reduce the likelihood of fraud. Our goal instead was to show—through an analysis of the application of GLP data on bisphenol A (BPA) in regulatory proceedings—that GLP by itself is insufficient to guarantee valid and reliable science. Becker et al. appear to have missed the point of our commentary entirely.
Why Public Health Agencies Cannot Depend on Good Laboratory Practices as a Criterion for Selecting Data: The Case of Bisphenol A
Myers JP, vom Saal FS, Akingbemi BT, Arizono K, Belcher S, Colborn T, Chahoud I, Crain DA , Farabollini F, Guilleffe LJ, Hassold T, Ho SM, Hunt PA, Iguchi T, Jobling S, Kanno J, Laufer H, Marcus M, Mclachlan JA, Nadal A, Oehlmann J, Olea N, Palanza P, Parmigiani S, Rubin BS, Schoenfelder G, Sonnenschein C, Soto AM, Taisness CE, Taylor JA, Vandenberg LN, Vandenbergh JG, Vogel S, Watson CS, Welshons WV, Zoeller RT. 2009. Environmental Health Perspectives 117(3):309-315; doi:10.1289/ehp.0800173.
Background: In their safety evaluations of bisphenol A (BPA), the U.S. Food and Drug Administration (FDA) and a counterpart in Europe, the European Food Safety Authority (EFSA), have given special prominence to two industry-funded studies that adhered to standards defined by Good Laboratory Practices (GLP). These same agencies have given much less weight in risk assessments to a large number of independently replicated non-GLP studies conducted with government funding by the leading experts in various fields of science from around the world.
Objectives: We reviewed differences between industry-funded GLP studies of BPA conducted by commercial laboratories for regulatory purposes and non-GLP studies conducted in academic and government laboratories to identify hazards and molecular mechanisms mediating adverse effects. We examined the methods and results in the GLP studies that were pivotal in the draft decision of the U.S. FDA declaring BPA safe in relation to findings from studies that were competitive for U.S. National Institutes of Health (NIH) funding, peer-reviewed for publication in leading journals, subject to independent replication, but rejected by the U.S. FDA for regulatory purposes.
Discussion: Although the U.S. FDA and EFSA have deemed two industry-funded GLP studies of BPA to be superior to hundreds of studies funded by the U.S. NIH and NIH counterparts in other countries, the GLP studies on which the agencies based their decisions have serious conceptual and methodologic flaws. In addition, the U.S. FDA and EFSA have mistakenly assumed that GLP yields valid and reliable scientific findings (i.e., “good science”). Their rationale for favoring GLP studies over hundreds of publically funded studies ignores the central factor in determining the reliability and validity of scientific findings, namely, independent replication, and use of the most appropriate and sensitive state-of-the-art assays, neither of which is an expectation of industry-funded GLP research.
Conclusions: Public health decisions should be based on studies using appropriate protocols with appropriate controls and the most sensitive assays, not GLP. Relevant NIH-funded research using state-of-the-art techniques should play a prominent role in safety evaluations of chemicals.
Pesticides, Sexual Development, Reproduction, and Fertility: Current Perspective and Future Direction
Colborn T, Carroll LE. 2007. Human and Ecological Risk Assessment 13(5):1078-1110; doi:10.1080/10807030701506405.
Improvements in chemical analytical technology and non-invasive sampling protocols have made it easier to detect pesticides and their metabolites at very low concentrations in human tissues. Monitoring has revealed that pesticides penetrate both maternal and paternal reproductive tissues and organs, thus providing a pathway for initiating harm to their offspring starting before fertilization throughout gestation and lactation. This article explores the literature that addresses the parental pathway of exposure to pesticides. We use DDT/DDE as a model for chemicals that oftentimes upon exposure have no apparent, immediate health impacts, or cause no obvious birth defects, and are seldom linked with cancer. Their health effects are overlooked because they are invisible and not life threatening—but might have significant health, social, and economic impacts at the individual and population levels. The purpose of this article is to demonstrate the necessity to develop new approaches for determining the safety of pesticides and the need for innovative regulatory policy to protect human and environmental health.
A Case for Revisiting the Safety of Pesticides: A Closer Look at Neurodevelopment
Colborn T. 2006. Environmental Health Perspectives 114(1):10-17; doi:10.1289/ehp.7940.
The quality and quantity of the data about the risk posed to humans by individual pesticides vary considerably. Unlike obvious birth defects, most developmental effects cannot be seen at birth or even later in life. Instead, brain and nervous system disturbances are expressed in terms of how an individual behaves and functions, which can vary considerably from birth through adulthood. In this article I challenge the protective value of current pesticide risk assessment strategies in light of the vast numbers of pesticides on the market and the vast number of possible target tissues and end points that often differ depending upon timing of exposure. Using the insecticide chlorpyrifos as a model, I reinforce the need for a new approach to determine the safety of all pesticide classes. Because of the uncertainty that will continue to exist about the safety of pesticides, it is apparent that a new regulatory approach to protect human health is needed.
Endocrine Disruption Overview: Are Males at Risk?
Colborn T. 2004. In: Hypospadias and Genital Development, Baskin L (ed), Kluwer Academic/Plenum Publishers, pp. 189-201; doi:10.1007/978-1-4419-8995-6_12.
The goal of this paper is to encourage physicians and others responsible for public health to start thinking outside of the box — to consider what has been learned from wildlife that has contributed considerably toward understanding the etiology of a number of human disorders that have increased significantly over the past 50 years in the developed world. Hopefully this will lead to practitioners’ thinking in broader terms when the etiology of a disorder is not evident. The increased incidence of hypospadias, for instance, would not have been discovered if it had not been for a troubled population of alligators in Lake Apopka, Florida. The reproductive success of the alligators had dropped to 10% and many of the males had undersized phalluses. These findings led to a series of laboratory studies that eventually revealed that there are synthetic anti-androgens in the environment that can interfere with male development and function. Serendipitous discoveries such as this concerning wildlife health have led to intense scrutiny concerning the etiology of a number of other human disorders related to the endocrine system such as abnormal sexual development and neurological and reproductive impairment.
Neurodevelopment and Endocrine Disruption
Colborn T. 2004. Environmental Health Perspectives 112(9):944-949; doi:10.1289/ehp.6601.
In this article I explore the possibility that contaminants contribute to the increasing prevalence of attention deficit hyperactivity disorder, autism, and associated neurodevelopmental and behavioral problems in developed countries. I discuss the exquisite sensitivity of the embryo and fetus to thyroid disturbance and provide evidence of human in utero exposure to contaminants that can interfere with the thyroid. Because it may never be possible to link prenatal exposure to a specific chemical with neurodevelopmental damage in humans, I also present alternate models where associations have been made between exposure to specific chemicals or chemical classes and developmental difficulties in laboratory animals, wildlife, and humans.