April 25, 2008

Purdue professor studies chemical compounds in plastics

"We are chronically exposed to low doses of multiple chemical compounds," says Gregory Knipp, an associate professor in the Department of Industrial and Physical Pharmacy. "While there has been a significant research focus on the individual effects of higher doses of chemicals, there is also a need to determine the effects of exposure to combinations of compounds at lower doses. By studying the interactions of these compounds, we can determine whether harmful effects of one compound are amplified by the presence of others."

There are more manmade chemical compounds in our environment now than ever before, and we are exposed to them by multiple pathways, Knipp says.

"In addition to the chemicals in plastics, foods can have chemicals to prolong freshness or residues of pesticides," he says. "We need to look into how prolonged exposure to small amounts of all of these compounds together affects our health."

Many plastics contain multiple manmade chemical compounds. For example, plastics that contain bisphenol A, or BPA, often contain phthalates as well, which are compounds that may be associated with neurodevelopmental disorders and cancer. Knipp's research group has collaborated with others to study the potentially harmful effects of phthalate-based compounds on pregnancy and fetal outcomes in rodents and is now studying the effects of combinations of phthalates and BPA.

"The effects of chemical compounds leaching out of plastics is clearly a major issue, but we need to keep in mind that individuals are likely not exposed to the high doses of these chemical compounds that are sometimes used in studies," he says. "Also, we need to be aware of the differences between acute exposure - a large amount in a short period of time - and chronic exposure -low doses day to day. These studies are our first recourse to check for potential harm, and additional studies are needed to know exactly where we stand."

Thomas Cook, an associate professor at Touro College of Pharmacy in New York who has collaborated with Knipp, says, "One of the main complexities regarding this issue is not only the effect of exposure to chemicals, but also that an individual's genetic makeup can play a major role in their toxic response to these chemicals."

Infants, children and pregnant women are most at risk for harmful effects from exposure to these compounds, Knipp says.

"The fetus and placenta tend to accumulate chemical compounds," he says. "There are higher levels of the proteins that bind drugs and nutrients in the fetal compartment. This helps protect the fetus and increase exposure to beneficial nutrients, but it also can increase exposure to harmful compounds."

Knipp and Cook plan to study lower levels of the compounds found in plastics, mimic the typical exposure level and examine the effects of exposure to multiple compounds at once.

"We need to determine what are the critical concentrations of these compounds, what are the more toxic combinations and what are the other critical factors that lead to adverse effects," Knipp says.

Writer: Elizabeth Gardner, (765) 494-2081, ekgardner@purdue.edu

Sources:   Gregory Knipp, (765) 463-1989, gknipp@pnhs.purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

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