Exposure to PCB’s May Interfere with Pregnancies
March 2, 2011 1 Comment
Wired.com
March 2, 2011
PCB exposure may interfere with a woman’s ability to get pregnant, a new study of women undergoing in vitro fertilization suggests. The study of 765 women found that those whose blood contained the highest levels of a particular form of polychlorinated biphenyl — one known as PCB 153 — were 41 percent less likely to give birth than women with the lowest levels.
One contributing factor: Fertilized eggs were half as likely to implant in women if blood concentrations of PCB-153 fell in the top 25 percent of those measured among all participants. The study appeared online Feb. 24 in Environmental Health Perspectives.
In women not undergoing IVF it would be difficult to know when to test for implantation, says John Meeker, who led the new study. So the new data may provide a window into a subtle fertility risk that would be almost impossible to find in the general population, explains Meeker, an environmental and reproductive epidemiologist at the University of Michigan School of Public Health in Ann Arbor.
His team studied blood and urine that had been collected from 765 women treated at fertility clinics in the Boston area between 1994 and 2003. Together, the women had gone through a total of 827 cycles of attempted fertilization — processes that led to 297 live births, 229 implantation failures and 301 pregnancies that naturally terminated within 20 weeks of implantation.
The researchers went into the study suspecting that the risk of implantation failure might be elevated among the most highly exposed women, based on earlier studies by others showing a similar problem in PCB-exposed rodents. Two years ago, Meeker’s team also showed that in women, PCBs can enter follicles, structures that hold egg cells. So this “does suggest that these chemicals can make it to a place where they would be in contact with the maturing egg,” he says.
More than 200 related PCBs exist. Most people inadvertently encounter a broad mix of these, including traces of PCB-153, through food and the environment. Because some of these pollutants are difficult and costly to measure in blood, the researchers tested for the sum of all PCBs as well as for a narrow spectrum of specific ones or mixes of several with related functional attributes, such as binding to hormone receptors in cells or — in PCB-153’s case — an ability to turn on certain detoxifying enzymes.
The authors caution that although they found the strongest signs of potential fertility risks associated with PCB-153, there were hints that other PCBs might also impair fertility. The team notes that PCB-153 might even serve as a marker for one or more other reproductively toxic PCBs — or related pollutants — that co-occur in the environment.
“I find the data intriguing — and think they have something here,” says David Carpenter, director of the Institute for Health and the Environment at the University at Albany in New York. “I’m also underwhelmed,” he adds.
The researchers probed for a number of different reproductive endpoints, he says, including miscarriage, and what are known as chemical pregnancies — where a fertilized egg dies before a fetal heartbeat can be detected. Only implantation failures appeared at rates greater than would be expected by chance. And only for PCB-153, he adds, not for any of several different PCBs or PCB combinations.
The data would be more convincing, Carpenter says, if the authors could point to some mechanism by which PCBs might impair reproduction — such as changing the permeability of the outer membrane of egg cells.
Several years ago, Carpenter’s team showed that some cells — nerve cells and immature immune cells — can incorporate PCBs, including PCB-153, altering the fluidity of the cells’ membranes. “Something as fundamental as changing the fluidity of the membrane in the oocyte [egg cell] or uterus could, in fact, have dramatic effects on implantation,” Carpenter says.
Until their U.S. production was banned in 1979, most PCBs were used as insulating liquids in electrical transformers. Over the years, PCBs also have found use in other applications, including as an ingredient of exterior building caulk and in some floor finishes. Because many PCB-containing materials are still in use and because any PCBs that enter the environment do not readily break down, people continue to encounter exposure to these potentially toxic compounds, most often through contaminated food.
About Luis Miranda
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PBC is made by Monsanto, it lines the cans of food we buy now, why? because they can no longer make PCB pipes which were once mandatory in New homes, I had them for about 4 months and they were awful , I had more floods because they would come apart and I would be standing at the kitchen sink in foot of water. I put in copper pipes after that. They had a factory that made these pipes in Alabama in the 40’s or 50’s and it contaminated this small towns well water,the river it was comin gfrom had bpc run-off coming from the PBC, most of the people in this town got cancer and died, it took 28 years for the remaining relatives to collect the money from a lawsuit they had going, the Government protected them then and they protect them now. when they finally had to pay. All of these pipes were proven carcinogenic and were removed from any new homes, they lay dormant for awhile until they showed up the last few years lining the tin cans your food is in, so much for the FDA. Yes this is the same BPC, its not the food that is infecting anything its the can the food is sitting in. Inmotion magazine had a 3 page article on this a few years ago, I saved it. I have stopped buying any canned goods that are lined with this stuff and I strongly suggest to anyone who finds this white plastic lining in their food cans not to buy the product and to write or call the company and tell them why, it won’t be the first foodline they have ruined, aspertame in gum is another Monsanto brainchild,they make it, it shows what kind of brains they have when they want you to let your children eat gum and candy with aspertame in it. I’ve been yelling about Flouride for years too and they finally are slowly removing it from the water supply , if that can really be done. I hope someone in the FDA goes after this food mafia, these thugs, of course it won’t really matter when the farm modernization act is implemented with the codex code in it, we’ll all die of starvation anyway.