By Janet Raloff
Late last week, California added diethylhexyl phthalate (DEHP)–a compound used to make plastics flexible–to the list of known reproductive toxicants regulated under the state statute called Proposition 65. Polyvinyl chloride (PVC) typically contains up to 40 percent DEHP. The chemical, which leaches out of PVC products such as blood-storage bags and intravenous tubing, can disrupt the normal development of male reproductive organs in animals (SN: 9/2/00, p. 152: New Concerns about Phthalates).
Manufacturers now have 1 year to label affected products to be sold in California as containing a reproductive poison. Neither the federal government nor any other state has acted against DEHP.
Concerns over DEHP’s migration from products and its toxicity prompted a team of engineers led by Jeongsoo Choi of Seoul (Korea) National University to develop a new class of plasticizers based on nontoxic compounds known as epsilon-caprolactone molecules, now used in such things as surgical sutures. He described the new additives’ performance 2 weeks ago at a conference on environmental hormones in New Orleans.
Choi’s team initially tried using an epsilon-caprolactone polymer that has a linear, chainlike molecular form. However, once added to PVC, the long molecules tangled, creating a product that was only 60 percent as plastic as the DEHP version. So, the Seoul team reengineered the epsilon-caprolactones into a treelike, “hyperbranched” polymer. Some 20 times as massive as the linear form, the newly patented compound doesn’t tangle, leaving PVC as flexible as if it were made with DEHP, Choi reported. More important, he told Science News, unlike DEHP, the new alternative “doesn’t migrate out–at all.”
His team is working with a Korean company to test the new PVC formulation in blood bags and food wrap.
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