October 19, 2011

from PreventDisease Website


Persistent organic compounds that are resistant to environmental degradation will soon have very significant impacts on human health with some scientists estimating that almost 50% of all babies worldwide will have at least one birth defect.

A variety of long-banned and currently-released chemicals found in pregnant women are associated with an increased risk of neural tube defects in their babies.


The chemicals known as persistent organic pollutants (POPs) include a variety of pesticides, industrial-use chemicals and compounds released from the burning of fossil fuels and other sources largely due to modern civilizations.

This study is the first to directly link placental levels of multiple POPs to neural tube defects.


The results strongly suggest that lingering environmental factors continue to damage fetal development and health.






"This is a serious concern," said Dr. Marvin Eastman from the Tobias environmental research centre in New York City.


"According to our research, in less than two decades the exponential rate of increase of POPs around the world will soon prevent almost half of newborns worldwide from developing normally and with at least one birth defect."

Many POPs are currently or were in the past used as pesticides.


Others are used in industrial processes and in the production of a range of goods such as solvents, polyvinyl chloride, and pharmaceuticals. Most POPs are created by humans in industrial processes, either intentionally or as byproducts.

POPs released to the environment have been shown to travel vast distances from their original source. Due to their chemical properties, many POPs are semi-volatile and insoluble. These compounds are therefore unable to transport directly through the environment. The indirect routes include attachment to particulate matter, and through the food web. The chemicals' semi-volatility allows them to travel long distances through the atmosphere before being deposited.


Thus POPs can be found all over the world, including in areas where they have never been used and remote regions such as the middle of oceans and Antarctica.


The chemicals' semi-volatility also means that they tend to volatilize in hot regions and accumulate in cold regions, where they tend to condense and stay. PCBs have been found in precipitation.

The ability of POPs to travel great distances is part of the explanation for why countries that banned the use of specific POPs are no longer experiencing a decline in their concentrations; the wind may carry chemicals into the country from places that still use them.

Researchers looked for an association between levels of POPs in the placenta of Chinese women who had just given birth and neural tube defects in their children.

Researchers examined 80 cases of fetuses or newborns with neural tube defects and 50 healthy controls from rural counties in the Shanxi Province in the People's Republic of China.


This province has the highest PAH emissions in the country. The pollutants in question are produced mainly from mining and burning coal. The Shanxi province also has the highest rates of neural tube defects in China at 14 per every 1,000 births.

At birth, the scientists measured several types of POPs in placental tissue, including 10 types of PAHs and multiple types of organochloride pesticides:

  • lindane (gamma-HCH)

  • two byproducts of alpha-HCH and beta-HCH, HCB and alpha-endosulfan

They also measured two types of the pesticide DDT and a number of DTT metabolites - the common chemicals produced when the body breaks down DTT.

Measuring levels of chemicals in the placenta is commonly used to approximate fetal exposure to chemicals. Investigators reported that some POPs were associated with a higher risk for carrying a baby with a defect. The strongest association was found with PAHs, chemicals that were detected in 82 to 100 percent of mothers-to-be.

Researchers found that moms that carried a baby with a neural tube defect were nearly five times as likely to have elevated levels of up to 10 different PAHs in their placentas.


What's more, the higher the level of placental PAHs, the larger the risk.

Citizens and habitats in most developed nations are at risk from POPs that have persisted in the environment from unintentionally produced POPs that are released locally and elsewhere and then transported by wind or water, for example, or from both. Although most developed nations have taken strong action to control POPs, a great number of developing nations have only fairly recently begun to restrict their production, use, and release.

Although scientists have more to learn about POPs chemicals, decades of scientific research have greatly increased our knowledge of POPs' impacts on people and wildlife. For example, laboratory studies have shown that low doses of certain POPs adversely affect some organ systems and aspects of development.


Studies also have shown that chronic exposure to low doses of certain POPs can result in reproductive and immune system deficits.


Exposure to high levels of certain POPs chemicals - higher than normally encountered by humans and wildlife - can cause serious damage or death. Epidemiological studies of exposed human populations and studies of wildlife might provide more information on health impacts. However, because such studies are less controlled than laboratory studies, other stresses cannot be ruled out as the cause of adverse effects.

To address this global concern, the United States joined forces with 90 other countries and the European Community to sign a United Nations treaty in Stockholm, Sweden, in May 2001. Under the treaty, known as the Stockholm Convention, countries agreed to reduce or eliminate the production, use, and/or release of 12 key POPs, and specified under the Convention a scientific review process that has led to the addition of other POPs chemicals of global concern.


Since 2001 POP proliferation has increased demonstrating the ineffectiveness of the treaty and lack of initiative by the United Nations.

Of the original 12 POPs covered by the Stockholm Convention, six are classified as carcinogens, according to the Eleventh Report on Carcinogens, published by the National Toxicology Program:

  • DDT

  • hexachlorobenzene

  • mirex

  • PCBs

  • TCDD dioxin

  • toxaphene

Lindane is also classified as a carcinogen.