NTP Draft Brief on DEHP
Barrett, Julia R., Environmental Health Perspectives
Questions about the safety of the plasticizer di(2-ethylhexyl) phthalate (DEHP), particularly in regards to exposure during medical procedures such as transfusions, have swirled for decades, but especially in the last several years, given growing concerns about endocrine disruption. In October 2005, an independent panel of experts convened by the National Toxicology Program Center for the Evaluation of Risks to Human Reproduction (NTP-CERHR) sought to take stock of what is known and identify critical research needs regarding human exposure to DEHP, in particular its potential reproductive and developmental toxicity. Now that the independent experts have had their say, the NTP is weighing in with its interpretation.
Based on the expert panel's report, comments from stakeholders and peer reviewers, and new information published since the experts' meeting, the NTP released a draft brief in May 2006 about DEHP exposure and toxicity. With peer review completed in late August, the brief is now being finalized and will be added to the forthcoming NTP-CERHR monograph The Potential Human Reproductive and Developmental Effects of DEHP.
This monograph will comprise the CERHR expert panel report, a list of the panel experts, all public comments made about the report, and the NTP brief on DEHP. Although the brief summarizes what the expert report says, it is more than just an executive summary--it represents the NTP's view of the various public and peer-review comments and additional research studies received since the report was prepared.
The 2005 expert panel meeting marks the first time the CERHR has had a compound re-evaluated; a previous evaluation was published in 2000. The need for another just five years later underscores the intensity with which DEHP is being investigated.
"[Assessing] DEHP again shows that the CERHR process is evergreen," says Paul Foster, deputy director of the NTPCERHR. "This is the first time that CERHR has gone back and said there's now been a significant amount of water that's gone under the bridge, and we should go back and re-evaluate to see whether or not any of our original conclusions have changed."
According to Foster, the brief distills the intricate and detailed scientific knowledge of the monograph into information that educated laypeople can use to put concerns about the potential for DEHP toxicity into perspective.
Hard Science on a Softener
DEHP is an oily chemical that confers flexibility to rigid polyvinyl chloride plastic. DEHP-softened plastic appears in numerous products, including building materials, food packaging, and medical devices. Because DEHP does not form tight chemical bonds with the plastic, some amount can leach out, and the compound has been detected in packaged foods, indoor air, household dust, and various substances and paraphernalia associated with medical treatment (such as bagged blood and tubing).
DEHP has induced reproductive and developmental problems in male rodents, but there are scant and uncertain data for effects in humans. It is known, however, that low-level human exposure is widespread and that certain populations are more highly exposed. For example, according to the draft brief, newborns and infants undergoing particular medical procedures may have 100 to 1,000 times the exposure experienced by the general population.
Because animal studies indicate that the developing male reproductive system is especially vulnerable to adverse DEHP-associated effects, the expert panel, in its 2005 report, attached "serious concern" to critically ill male newborns and infants receiving prolonged medical treatment. The NTP concurred in its draft brief and also agreed that concern is warranted for male infants younger than 1 year and for the sons of women who underwent certain medical procedures while pregnant. Less concern was attached to low-level exposures in utero or after the first year of life, and there was minimal concern for adverse effects from typical background exposures. …