Tags: Chronic Hazard Advisory Panel, phthalates
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written by Ted Schettler, MD, MPH
Science Director for CHE and the Science and Environmental Health Network
Phthalates are a family of chemicals used in many consumer products, mainly as softeners of plastics and sometimes as solvents. As a result, human exposures are ubiquitous. In recent years, many laboratory and epidemiologic studies have shown that some phthalates can cause a variety of adverse health effects. In response, the 2008 Consumer Product Safety Improvement Act (CPSIA) permanently banned three phthalates and temporarily banned three additional phthalates from use in children’s toys and child care products while calling for an expert scientific review of phthalate-related risks.
A panel of scientists assembled as members of the Chronic Hazard Advisory Panel (CHAP) and charged with assessing the safety of using phthalates or six alternative chemicals in children’s toys and child care articles has completed their review and released a report. They recommended that current bans on four phthalates should be permanent, four additional phthalates should be banned, and current bans on two should be lifted. Further, because of inadequate safety information, the panels says governmental agencies should obtain necessary exposure and hazard data for other phthalates and alternatives in order to assess health risks, as they are charged and authorized to do.
Health effects of phthalates
The panel acknowledged a variety of health effects linked to exposure to phthalates and decided that the greatest concern is that some can be harmful to male reproductive organ development, particularly following exposure during late gestation and the early postnatal period. These findings are well established in studies of laboratory rats. Malformations of the epididymis, vas deferens, seminal vesicles, prostate, external genitalia (hypospadias), and cryptorchidism (undescended testes) as well as retention of nipples/areolae and demasculinization of the perineum, resulting in reduced anogenital distance (AGD) are described after exposure to phthalates with three to eight carbon atoms in the backbone of the chemical compound. Some, but not all, studies suggest similar effects in humans, including reduced AGD, hypospadias, poor sperm quality, and reduced fertility. Although the panel focused on these anti-androgenic effects of phthalates, they noted that several studies in humans also identified impaired neurobehavioral development in children with higher exposure levels.
Animal vs. human studies of phthalate effects
The panel reviewed apparent species differences in response to phthalate exposure. In animal studies, rats seem to be most sensitive while mice, guinea pigs, hamsters, and non-human primates are variably less vulnerable. Experimental studies with human fetal tissues are inconclusive, but the panel said epidemiologic studies showing reduced anogenital distance in baby boys associated with higher prenatal phthalate exposure is “a robust read-out of diminished androgen action in utero, and these observations give strong indications that phthalates are capable of driving down fetal androgen synthesis in humans.” Thus, they concluded, studies in rats currently offer the best available data for assessing human risk.
Human exposure to phthalates
The panel used biomonitoring studies and scenario-based exposure assessments to estimate human exposures to phthalates. The scenario-based estimates of exposure were made for individual sources such as toys, personal care products, and household products. Exposure was estimated from information on phthalate concentrations in products and environmental media, frequency and duration of contact with products and environmental media, and physiological information. Overall, food, beverages, and drugs via direct ingestion, and not children’s toys and their personal care products, constituted the highest phthalate exposures to all subpopulations, with the highest exposure being dependent upon the phthalate and the products that contain it.
The panel found that most people are exposed to multiple phthalates. Studies in rats have shown that mixtures of phthalates act in an additive fashion in causing male reproductive tract effects. Thus, the assumption of dose addition is appropriate for mixtures of phthalates in order to assess risk. Taking into account uncertainties, the panel estimated that roughly 10 percent of pregnant women in the US are exposed to phthalates above safe, acceptable levels. This means that efforts must be strengthened to reduce exposure to phthalates from all sources associated with adverse impacts on fetal, infant, and child development.
Expert panel recommendations
The panel’s assessment is divided into four categories: 1) phthalates already permanently banned by the Consumer Product Safety Improvement Act (CPSIA), 2) phthalates subject to an interim ban, 3) phthalates not regulated by the CPSIA, and 4) phthalate alternatives. They recommend:
- No further action by the Consumer Product Safety Commission on dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), or di(2-ethylhexyl) phthalate (DEHP) at this time because they are already permanently banned in children’s toys and child care articles at levels greater than 0.1 percent.
- The interim ban on the use of diisononyl phthalate (DINP) in children’s toys and child care articles at levels greater than 0.1 percent be made permanent.
- The current bans on di-n-octyl phthalate (DNOP) and diisodecyl phthalate (DIDP) be lifted
- No action on dimethyl phthalate (DMP) or diethyl phthalate (DEP).
- Diisobutyl phthalate (DIBP), di-n-pentyl phthalate (DPENP), di-n-hexyl phthalate (DHEXP), and dicyclohexyl phthalate (DCHP) should be permanently banned from use in children’s toys and child care articles at levels greater than 0.1 percent because they contribute to the cumulative risk of exposure to other phthalates with similar toxicity profiles
- An interim ban on diisooctyl phthalate (DIOP) in children’s toys and child care articles until its toxic properties are better understood.
- Appropriate agencies obtain the necessary exposure and hazard data to estimate total exposure to phthalate alternatives and assess the potential health risks.
The panel’s report is notable for several reasons:
- It follows the recommendations of the National Academy of Science’s report on assessing cumulative risks from exposures to harmful chemicals from multiple sources.
- It repeatedly emphasizes the need for additional US agencies responsible for oversight of other phthalate-containing products to step up and conduct necessary risk assessments with the goal of risk management.
- It underscores the need for additional toxicological and exposure data to help agencies better understand the risk of some phthalates and their alternatives and take risk management steps as necessary to protect public health.
What it means
This report is a case study in many of the shortcomings of chemical management programs in the US. People are exposed to multiple chemicals, from multiple sources, with similar kinds of health effects. These exposures are sometimes at unsafe levels. How common is that? Unfortunately, all too often we don’t know since, until now, with few exceptions, no effort has been undertaken to assess the cumulative risk. Even worse, many chemicals in consumer products have not undergone safety testing at all, and there is no pre-market requirement for manufacturers to do that. This means that people are the guinea pigs, and it’s up to government regulators, academic scientists, and nongovernmental organizations to press for and carry out testing long after our families and communities have already been exposed. It makes no sense.
Hopefully, this panel’s report will encourage strengthened efforts to reform chemicals management in the US with a strong emphasis on protecting public health, based on modern science, and giving the benefit of doubt to particularly vulnerable fetuses, infants, children, and adults when confronting scientific uncertainty. Scientific understanding of chemical toxicity and exposures is always evolving. But, as the panel noted, we must use the data we currently have to assess human risk. And we must also create incentives and requirements for acquiring safety data to avoid unnecessarily exposing entire generations of people to chemicals at levels that, too often, are much later revealed to be dangerous.
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written by Martha Herbert, PhD, MD
This excerpt from Dr. Herbert’s blog is shared with her permission. Read the full post on her blog.
The recent New England Journal of Medicine paper by Stoner and colleagues, “Patches of disorganization in the neocortex of children with autism.” N Engl J Med 370(13): 1209-1219, made several important contributions to studies of postmortem tissue samples from the brains of individuals with autism spectrum disorders (ASDs). First, the average age was much younger than the average age in previous studies. Second, many important and technologically sophisticated measures were made. Finally, as a result of this work, a broadly distributed pattern of brain tissue abnormalities was identified that had not been described on this scale before—namely, patches of disorganization in many areas of the neocortex (the outer layer of gray matter in the brain), though not the same from one person to the next.
The new observation of disorganized patches by itself is very important. It poses an important challenge: how do we figure out what it means? To do that, we need to understand the data, and also to examine the interpretations and consider alternative possibilities.