Public concern has been raised recently regarding the possible health hazards of di(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DINP), two chemicals used as plasticizers in flexible vinyl products. DEHP is the primary plasticizer used in many medical devices, whereas DINP serves a similar function in soft vinyl toys that may be mouthed by young children.
In response to these concerns, the American Council on Science and Health convened a 17-member independent expert panel, chaired by former U.S. Surgeon General C. Everett Koop, to investigate this issue. Nationally and internationally recognized scientists and physicians, with expertise in a range of relevant disciplines–including pediatrics, toxicology, metabolism, epidemiology, risk assessment, and medicine–comprised the investigating panel.
The panel’s charge was twofold. First, it was to evaluate the scientific evidence regarding potential health risks associated with DEHP and DINP. Second, it was to identify areas of uncertainty or data gaps in the information available on these substances.
Panel members reviewed a wide variety of documents, including primary and secondary scientific literature, risk assessments published by regulators in the U.S., Canada, and Europe, and scientific manuscripts still in preparation, to ensure that their consensus statement would reflect the most recent studies. In addition, the members of the panel reviewed source information that forms the basis for concerns about human health effects of DEHP and DINP.
There are always uncertainties and assumptions involved in any risk assessment. Hence, it is impossible to state that there is no risk from exposure to a given substance. The same observation, however, is applicable to the vast number of chemicals that occur naturally and to which humans are exposed. A risk assessment that considers and utilizes the weight of scientific evidence can minimize uncertainty about potential human risks.
Accordingly, the conclusions of the independent panel are based on two main parameters. First, the panel found scientific data and analyses indicating that:
- DEHP and DINP are not genotoxic;
- an exposure to each can be estimated below which effects are unlikely to occur, and
- there are critical differences between rodents and humans in the toxicology and mechanisms of action for these chemicals.
The panel also based its evaluation on measurements or estimates of human exposure to DEHP and DINP.
The panel concluded that DEHP in medical devices is not harmful to even highly exposed people; that is, those who undergo certain medical procedures, such as regular hemodialysis. Furthermore, the panel concluded that DEHP has a variety of important physical characteristics that are critical to the function of medical devices, and that eliminating DEHP in these products could cause harm to some individuals.
Any substitute for DEHP or DEHP-containing medical devices thus should be evaluated using the same criteria as used for DEHP. These criteria are: (a) demonstrated suitable physical characteristics and function in critical medical device applications, and (b) risk assessment based upon studies of animal and human toxicology and human exposure data.
The scientific literature on DINP is less voluminous than that on DEHP. Although results of animal toxicity tests suggest the need for thorough evaluation, the panel concluded that much of this evidence has little relevance for humans, and that DINP in toys is not harmful for children in the normal use of these toys.
To expand our knowledge on child exposure to DINP from toys, the panel recommended that further studies be undertaken to document (a) children’s contact time and mouthing behavior with toys and other objects, and (b) rates of release of DINP under realistic conditions. This would improve the precision of exposure estimates for DINP, and would also be of benefit in evaluating exposures to other substances in toys or objects mouthed by children.
As with DEHP, any substitute for DINP or DINP-containing flexible toys should be evaluated for potential risks based on animal and human toxicology data and human exposure data.
In summarizing the panel’s report, panel chairman Koop said, “Consumers can be confident that vinyl toys and medical devices are safe. The panel’s findings confirm what the U.S. FDA and the Consumer Product Safety Commission have been saying about these products all along. There is no scientific evidence that they are harmful to children or adults.”
For more information …
The full ACSH report, “A Scientific Evaluation of Health Effects of Two Plasticizers Used in Medical Devices and Toys,” is available to registered Medscape users at http://www.Medscape.com. A complete list of panel members is available at http://www.acsh.org/press/releases/koop021299.html. The executive summary is available at http://www.drkoop.com/healthnews/special-reports/acsh/June/phthalate.html.
