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In the largest study to date on phthalates and postmenopausal bad cancer, a cancer epidemiology researcher from the University of Mbadachusetts at Amherst found no badociation between cancer risk bad and exposure to plasticizers and solvents used in common products such as shampoo, makeup, vinyl flooring, toys, medical devices and car interiors.
Posted in Journal of the National Cancer Institute, the research "excludes any extreme increase in risk," but still leaves open the question of whether there is a relationship between phthalate exposure and bad cancer, says Katherine Reeves, badociate professor at the School of Public Health and Health Sciences.
"Our research has raised almost as many questions as answers," said Reeves, whose study was funded by a $ 1.5 million grant over three years, awarded by the National Institute of Physicians and Surgeons. environmental health sciences. "I think it's an important contribution to the literature, but there is still a lot of work to be done, especially with regard to younger women."
In the United States, virtually everyone is exposed to varying degrees of phthalates, mainly by eating and drinking food and liquids that have come into contact with products containing chemicals, according to a fact sheet from the Centers for Disease Control and Prevention. After ingestion, the body breaks down phthalates into metabolites that are rapidly excreted in the urine and can be badyzed. "If you excrete more, you're probably exposed to more," says Reeves.
For their prospective study, the first to measure phthalate exposure prior to a cancer diagnosis, colleagues at Reeves and UMbad Amherst turned to the Women's Health Initiative (WHI), a long-term national health study. involving more than 160,000 postmenopausal women. Prospective cohort studies allow researchers to calculate the incidence of the disease in an appropriate temporal sequence, establishing the level of exposure before knowing the results, which provides stronger evidence than others types of studies.
Researchers at UMbad Amherst examined the concentrations of 11 metabolites of phthalates in urine samples of 419 women in whom invasive bad cancer had been diagnosed after the third year of WHI. They also studied samples of 838 healthy women who did not develop bad cancer.
Two or three urine samples from each participant – from baseline, year 1, and year 3 – were measured, which addresses two of the challenges related to Study of phthalate exposure, says Reeves. Previous studies had examined urine samples after a diagnosis of bad cancer, when the exposure could come from medical equipment or medication. In the Reeves study, "the samples were collected when everyone was healthy, which gave us samples without fear that the differences in exposure could be related to diagnosis and treatment" .
In addition, the badysis of several urine samples should increase the chances of obtaining a more accurate picture of the exposure. Half of the phthalate metabolites are excreted in the urine within 12 to 24 hours of exposure, says Reeves. "If you rely on a single measure, you risk misclbadifying people and not getting badociation or getting the wrong badociation."
Although the researchers badyzed several urine samples taken from each person a few years apart, Reeves said the study had limitations. "The exposure of people to phthalates changes enough over time, and so it's hard to characterize the most exposed and exposed people." That's what we need to be able to do to badess whether a higher exposure to phthalates is related to the risk of bad cancer, "said Reeves. "The use of two to three samples per person helped, but it was not totally able to overcome this challenge."
Reeves says that future research would benefit from studying younger women. "The most critical period for the development of bad cancer is in previous years." Watching women aged 50 to 60 may not be the most important period of exposure, "she says.
Additional urine samples – perhaps 10 to 20 – would allow researchers to characterize the exposure more accurately as being low, medium or high. The study also recommends that future research look more closely at postmenopausal women who are not on hormone replacement therapy, as "some potentially positive, but not statistically significant badociations" have been found between the level of phthalate metabolites and the risk of bad cancer in this subgroup.
"We need to know the answer to find out if these chemicals cause or do not cause bad cancer or other health problems," said Reeves. "It's an urgent problem and we are trying to come up with creative solutions to get not just an answer, but the right answer."
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