In the wake of a recent government report showing a link between cancer and a commonly used chemical found in many plastic products -- including infant toys and pacifiers -- two main questions remain: Will the chemical, known as DEHP, be regulated, and what, if anything, should consumers do to minimize exposure?
Neither question is easy to answer.
In the next few months, the Consumer Product Safety Commission will review the report from its Chronic Hazard Advisory Panel "and consider what, if any, action may be necessary regarding products containing DEHP," CPSC chairman Terrence Scanlon said in a statement last week.
At this point, attempting to minimize exposure to DEHP is "premature," says advisory panel chairman Richard A. Griesemer, formerly with the National Cancer Institute and now a veterinarian and pathologist with the Oak Ridge National Laboratory in Tennesee.
DEHP is the shorthand name for the chemical di(2-ethyhexyl)phthalate, a substance that's been used for some 40 years as a softening agent for such commonly used plastics as polyvinyl chloride.
"All of us are probably exposed to small amounts of DEHP because it's so widely used in the environment," says Griesemer.
It's DEHP that gives telephone cords their flexibility and makes the tubing for kidney dialysis machines so pliable, and DEHP is in the plastic bags used for storing blood and platelets.
"Platelets have a much longer lifetime in DEHP bags than they do in anything else," says Langley Spurlock, organic chemist and director of Biomedical and Environmental Science at the Chemical Manufacturers Association. Pints of blood also have a longer shelf life in these DEHP-containing bags, Spurlock says, and "there's no known substitute for them."
DEHP also is found in shower curtains, vinyl wall coverings and some plastic products used by infants and children.
But despite its widespread use, studies suggest that DEHP causes cancer in rats and in mice -- a finding with such concrete scientific documentation that neither the Society of Plastics Industries nor the Chemical Manufacturers Association disputes it.
It is this association with cancer that caused the CPSC to publish a notice in the December 1983 Federal Register expressing concern that the current use of DEHP as a softener, or "plasticizer," in children's products "may result in a substantial exposure of children to a substance that is reported to cause cancer in animals," the report notes. "The potential health hazard to children is believed to result from exposure to DEHP contained in plastic articles such as pacifiers, squeeze toys, plastic baby pants and the vinyl fabric covering of playpen pads or similar articles."
Based on this scientific evidence, the Consumer Product Safety Commission asked the Chronic Hazard Advisory Panel to examine DEHP and its potential health effects on consumers. Results of the report were released last week and again, after reviewing the scientific literature, the panel concluded that the chemical:
*is "readily absorbed" after ingestion and can also be absorbed at much lower levels through skin contact. Sucking or teething on pacifiers or toys can be a source of ingestion, the report says;
*causes liver cancer in mice and rats after lifetime exposure;
*can cause reduced fertility and testicular atropcy in male rodents. In pregnant female animals, DEHP caused birth defects;
*is not mutagenic; that is, DEHP does not cause cancer by damaging DNA or chromosomes.
People likely to receive the most exposure to DEHP, the panel concluded, are the 3 million patients who receive blood transfusions each year, the 50,000 people who undergo kidney dialysis, the 10,000 hemophiliacs who receive platelets or other blood products, and children -- an estimated 3.5 million newborns -- who may ingest the chemical by sucking on DEHP-containing pacifiers or toys.
Yet experts, including advisory panel chairman Griesemer, are quick to note that benefits far outweigh the risks for dialysis patients, hemophiliacs and people requiring blood transfusions.
"We're only talking theoretical risk," Griesemer says. "This is based on a lot of assumptions. I wouldn't want to alarm such people. I wouldn't want them to stop their treatment."
The Chemical Manufacturers Association's Spurlock says "the thing to remember is that DEHP does cause cancer in rats and mice, but only in extremely high doses" -- about "4 million times" the exposure that most people can expect to receive.
No one understands exactly how DEHP causes cancer. "It's really a scientific curiousity, one that's turned out to be an interesting research question," Spurlock says.
Many cancer-causing chemicals act by causing damage to the genetic material in cells, the deoxyribonucleic acid, or DNA. But not DEHP. The theory is that DEHP causes cancer by producing excess amounts of tiny microbodies in the liver called peroxisomes. Normally, these structures help process dietary fat and give off peroxide as a by-product of their fat digestion.
DEHP causes a proliferation of peroxisomes in rats and mice, and as a result an excess amount of peroxide production. "It is this peroxide that seems to be leading to cancer in rodents ," Spurlock says.
Whether DEHP acts the same way in humans is not known. Studies of DEHP in monkeys have not produced cancer. "People that I've talked to are really concerned about not having this blown out of proportion," says Gregory Cramer of the Food and Drug Administration.
Adds Griesemer: "There's really no evidence that DEHP and other plastics are causing cancers in the United States." What's really needed, he says, "is continued surveillance."
"For perspective," Griesemer says, "DEHP is of no concern compared to the health risks of cigarette smoking or asbestos exposure, both of which are enormous health problems."