Proof: PCBs Hazardous to humans

April 19, 2009

Proof is in the poison: PCB toxins are hazardous to humans

Studies: Even low levels alter brain's development

By Tony Walter

The jury's decision on human health hazards of PCBs came in a long time ago.

They harm everyone from the unborn to the elderly, causing cancer and damaging immune and reproductive systems. Scientific studies have shown for decades that the toxins poison the environment, and data now exist showing they harm humans.

Three new studies by researchers at the University of California-Davis, and Harvard University concluded that even low-level exposure to PCBs, like the kind scheduled to be removed from the Fox River at the end of the month, likely contributes to developmental disorders in children, including autism, attention deficit disorder, learning disabilities and mental retardation.

The results of all three studies were made public in the last month and included tests on rats, with researchers mimicking in the animals low-level PCB exposure that children experience.

Isaac Pessah, director of the UC-Davis Center for Children's Environmental Health, and co-author of all three studies, said results of the tests on rats can be translated to show the toxins' impact on the human brain.

The study by UC-Davis researchers showed that low-level pre-birth and neonatal exposure to PCBs altered the development of brain cells in rats.

Another study by the same research team showed that PCBs affected the region of the brain known to be impaired in several disorders including autism.

The third study, collaborative work between UC-Davis and Harvard researchers, showed that PCBs likely contribute to overexcitability in the brain, which produces attention deficit and learning disabilities.

"We've never really understood the mechanism by which PCBs produce neurobehavioral problems in children," Pessah said. "One of the most difficult processes we are faced with is basing our science on models. (But) with these studies we have shown how PCBs alter the development and excitability of brain cells."

Unknown impact

The Fox River cleanup is expected to last a decade, but the impact of the toxin on several generations won't be known until long after the sediment has been dredged from the river or left on the riverbed and capped with sand and gravel.

Eight paper companies along the Fox River used PCBs — polychlorinated biphenyls — to produce carbonless copy paper beginning in the 1950s. The federal government banned them in 1977 after it was discovered that the toxins were a likely cause of cancer and a proven threat to wildlife.

In the 1990s, state and federal environmental agencies ordered the paper companies that dumped PCB waste into the river to clean it up. The process has been slowed because of lengthy court battles over financial responsibility for the project.

Although early studies pointed toward the likelihood that PCBs cause cancer in humans, later studies show the negative health effects are more widespread.

There have been countless studies of the impact of PCBs on human health, but the gold standard was published in The New England Journal of Medicine in 1996.

Wayne State University psychologists Joseph and Sandra Jacobson traced the impact on 242 children whose mothers had eaten salmon and lake trout from Lake Michigan an average of two to three times a month for about six years before giving birth.

At age 11, the children whose mothers had eaten greater quantities of the fish had lower IQs, poorer reading comprehension, more difficulty paying attention, and greater memory problems, the study found.

Effect on Laotian, Hmong studied

Ongoing studies led by Green Bay native Susan Schantz, a professor of veterinary biosciences at the University of Illinois and director of the Fox River Environment and Diet Study (FRIENDS), are examining the effects of the exposure to PCBs in fish eaten in large quantities by Laotian and Hmong refugees in Green Bay and Appleton.

Vue Lor, information and assistance specialist for the Aging and Disability Resource Center of Brown County and former president of the Hmong Association of Green Bay, served on an advisory committee for FRIENDS and helped recruit Hmong families for Schantz's study.

"The older generations … weren't accustomed to (blood) testing, and they didn't know they shouldn't eat the fish. But education made a large impact and people said, 'Oh, my goodness, I didn't know that,'" Lor said.

Schantz said the research has shown that Hmong or Laotians who ate larger quantities of fish from the Fox River, Oconto River and Lake Michigan have higher levels of PCBs in their bodies.

Just 2 percent of all cancer is caused by environmental pollution, according to the 2002 Harvard Report on Cancer Prevention. Brown County's cancer incident rate of 483.2 per 100,000 population is below the state average of 483.4. Oconto (472.5) and Shawano (478.4) counties are also below the average, but Kewaunee (509.5) and Door (536-5) counties are above the average, according to American Cancer Society statistics for 1999-2003.

Advisories issued

It has been 33 years since the DNR issued its first fish consumption advisory in response to studies by public health, water quality and fisheries experts. The warning was issued after it was learned that fish store PCBs in their fatty tissue.

The DNR recommends no more than one meal per month of most fish caught in the Fox River from Little Lake Buttes des Morts to the river's mouth in Green Bay and warns people not to eat any carp, catfish or white bass, or any walleye longer than 22 inches.

The agency also suggests that white perch, white suckers, northern pike longer than 33 inches, and sheepshead at least 10 inches long should be eaten only once every two months.

The warnings haven't stopped fishermen from plying their sport on the river despite the fish advisory that will probably remain in effect for several years. DNR warden Ben Treml said he thinks most people catch the fish for the sport or for mounting.

"It's a great fishery but not for eating," said Matt Gaede of Eau Claire as he prepared to launch his boat at Fox Pointe Boat Launch in De Pere this week.
Additional Facts
PCB health risk

The Agency for Toxic Substances and Disease Registry, based in Atlanta, is a federal public health agency of the U.S. Department of Health and Human Services. It produced the following summary in its "Public Health Implications of Exposure to PCBs" 2002 study.
# Susceptible human populations are being exposed to PCBs via fish consumption.
# Many residents in the Great Lakes basin ate more fish than the 6.5 grams a day often estimated for the general U.S. population.
# High consumption of PCB-contaminated Great Lakes sports fish is associated with increased body burden levels of PCBs.
# These body burden levels are higher than in the general U.S. population.
# Men eat more fish than women eat, and both men and women eat Great Lakes fish during most of their reproductive years.
# Neurobehavioral and developmental deficits occur in newborns exposed in utero to PCBs and continue in school-aged children.
# Reproductive function might be disrupted by exposure to PCBs, although more research is required to resolve this possibility.
# Exposure to PCBs in fish places adult men, women beyond their reproductive years, and the elderly at increased risk for cancer. They might also be at increased risk for immune and endocrine system effects.
# Exposure to PCBs might increase the risk for clinical effects such as non-Hodgkin's lymphoma, diabetes, and liver disease.
# As research progresses, more will become known about the human health implications of PCBs and other contaminants found in the environment. However, enough scientific information is now available to warrant actions by health care providers, public health officials, and environmental organizations.
— U.S. Department of Health and Human Services