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有毒的遗产: 农药危害影响三代人  

2014-09-11 17:52:11|  分类: 环境与健康 |  标签: |举报 |字号 订阅

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During the 1950’s and 1960’s, DDT was the “go-to” pesticide in the United States – until its toxicity caused it to be banned. Methoxyclor, billed as a “safer” alternative to DDT, then took center stage. Marketed under a variety of names – including Methoxo, Metox, Chemform and Moxie – the chemical was sprayed lavishly on food crops, garden plants, farm animals and household pets.

Now, emerging research demonstrates that methoxyclor – although banned since 2003 – has left a chilling legacy of disease spanning three generations.

A study conducted at Washington State University and published in the latest edition of the scientific journal PLoS ONE raises the possibility that a pesticide your great-grandmother was exposed to during pregnancy can result in a dramatic increase in your own vulnerability to developing certain conditions, including adult onset kidney disease, ovarian disease and obesity. Even more disturbingly, you can pass the diseases on to your grandchildren.

The researchers, led by Michael Skinner – a professor of molecular biology and founder of WSU’s Center for Reproductive Biology – examined the effects of methoxyclor on generations of rats. Due to their abbreviated lifespans and rapid reproductive rates, rats are commonly used for generational studies.

Scientific research results reveal grim implications for human health

The team found that when pregnant rats were exposed to methoxyclor, at concentrations typical of high environmental exposures, three generations of the rats’ offspring had a higher incidence of kidney and ovarian disease, as well as an increased propensity for obesity. Ominously, the effects weren’t diluted by the passage of time and the birth of new generations.

The “great-grandchildren” of the exposed rats had increased incidence of multiple diseases – even though pesticide exposure was limited to what was experienced by their ancestors. This research is important, because it demonstrates that pesticides may affect how genes are turned off and on in the progeny of exposed animals – a phenomenon known as transgenerational epigenetic inheritance.

Scientists have previously documented that this type of epigenetic inheritance can result from a variety of environmental toxins. In addition to DDT and other pesticides, fungicides, dioxins, bisphenol-A and hydrocarbons have been implicated. However, this research is the first to show that the majority of transgenerational epigenetic inheritance traits are passed primarily through the female line.

This doesn’t mean that males are unaffected. The study revealed that male rats that were great-grandchildren of the exposed female rats had mutations in the sperm epigenome – which regulates gene expression.

Could methoxyclor be causing the national epidemic of obesity and disease?

The bad news on methoxyclor exposure isn’t confined to rats, of course. Experts say that methoxyclor behaves like estrogen in the body – as a result, it can profoundly affect the reproductive system.

People exposed directly to the pesticide can experience fertility problems and an increased vulnerability to adult onset disease, as well as the potential to pass on the conditions – a possible factor in the unprecedented rise in obesity in North America.

Earlier studies show generational risks from other toxic chemicals

A 2013 WSU study helmed by Skinner and published in PLoS ONE identified significant increases in obesity and reproductive disease as transgenerational threats in rats exposed to the industrial chemical bisphenol-A, or BPA. The first and third generations were affected.

The first generation, rats whose mothers had been exposed during gestation, had a higher incidence of kidney and prostate disease. The third generation, the “grandchildren” of the first generation and the “great-grandchildren” of the exposed generation, had reproductive disease and obesity, even though they had had no direct exposure to environmental toxins.

A related study, published in 2013 in Reproductive Toxicology, exposed pregnant female rats to hydrocarbons. Again, higher rates of disease were seen in first and third generations.

The long-term effects of methoxyclor should be no surprise – thanks to DDT

Dichlorodiphenyltrichloroethane – shortened to DDT, for obvious reasons – has been linked to breast and other cancers, miscarriages, low birth rate, developmental delays, and liver damage. And, almost 40 years after being banned, DDT can still be found in our food supplies – and lingering in our bodies.

According to Pesticide Action Network, breakdown products of DDT can be found in 60 percent of heavy cream, 42 percent of all kale greens, and 28 percent of all carrots. In addition, DDT breakdown products can be identified in the blood of 99 percent of all people tested.

Alarmingly, the President’s Cancer Panel reports that girls exposed to DDT before puberty are five times more likely to develop breast cancer in middle age.

Let’s not forget the long-term dangers posed by pesticides

Currently, DDT – sprayed indoors – is still legal for use in malaria control in sub-Saharan Africa. While Pesticide Action Network and other environmental groups want its use phased out, DDT proponents argue for more widespread use. PAN insists that there are safer and more effective methods of control, and points to successful non-DDT techniques currently used in Kenya, Mexico and Vietnam.

It’s worth remembering: these studies aren’t the work of alarmists trying to frighten the public. Funded by the National Institutes of Health, published in peer-reviewed journals and conducted by respected scientists, the research offers a sobering look at the cost – to both current and future generations – of using toxic chemicals.

References:
http://www.sciencedaily.com/releases/2014/07/140724144253.htm
http://www.panna.org/issues/persistent-poisons/the-ddt-story
http://www.sciencedaily.com/releases/2013/01/130124183630.htm

Aug. 25, 2014 by Karen Sanders

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