Native American teenagers have legacy of PCB pollution

Decades after fish and wildlife advisories went into effect, industrial pollutants found in the blood of Native American youths and young adults show that the younger generation is still at risk from long-banned contaminants.

 Teenagers from the Akwesasne Mohawk Nation in New York state had PCB concentrations twice the national average, when compared to a U.S. Centers for Disease Control and Prevention national survey.

 Significantly higher amounts were found in first borns, those who were breast-fed and those who ate fish in the prior year. Levels were also higher in those born before the advisory that recommended against eating their traditional fish and animal foods, the University of Albany study finds. The results are published in the journal Chemosphere.

More than 25 years ago, members of the Akwesasne Mohawk Nation were told to alter their traditional way of life and not eat locally-caught fish and wildlife due to persistent organic pollutant (POPs) contamination. The change led to reduced local fish consumption rates in the tribe that paralleled a decrease in polychlorinated biphenyl (PCB) concentrations in breast milk during the 1990s.The Akwesasne Mohawk Nation is located in northern New York state and the Canadian provinces of Quebec and Ontario. The Territory is adjacent to a 270-acre U.S. Environmental Protection Agency Superfund hazardous waste site that housed a General Motors foundry, which used PCB-containing hydrologic fluid in factory machinery. Additionally, aluminum smelters that operated on nearby property – now two New York state Superfund sites –  also contributed PCBs that contaminated the local waterways. These polluted sites lie on the St. Lawrence River just upstream from the Akwesasne Mohawk Nation reservation.

In short, PCBs contaminate the local environment, wildlife and the Mohawk people.

PCBs were synthesized and used mainly in complex mixtures for a wide range of commercial and industrial applications, including transformers, electronics, florescent light fixtures, lubricants, plastics and pigments. The more than 200 varieties vary in toxicity and longevity – some persist for decades or centuries while other break down in months or years.

Production was banned in the United States in 1979. Even though their use is curtailed, they continue to contaminate food, soil, water, animals and people. These very stable chemicals do not readily break down, leading to persistent pollution. PCBs accumulate in body fat. Body levels increase with continued exposure, mainly through fish, plants and other foods.

Many health effects are linked to PCB exposure. Studies with people and animals show exposure can cause cancer and impact the functioning of reproductive, developmental and endocrine systems.

They gathered demographic, lifestyle and diet information through interviews and questionnaires. Included were fish consumption, cigarette and alcohol use, breast-feeding history, educational status and birth order.

In addition, daily diet information – items, frequency, portion size – was reported using the Food Frequency Questionnaire developed by the National Cancer Institute and the U.S. Department of Agriculture.

POPs levels measured in the blood were compared to national averages of 12- to 19-year-old youth measured during a Centers for Disease Control and Prevention study on human body burdens of environmental chemicals (Centers for Disease Control 2009). They were also compared to several variables that might be associated with the PCB levels, such as sex, breast-feeding status, sociodemographics and diet.

What did they find?

While all of the Mohawk youths tested had some PCBs in their blood, 17 PCB types were measured in more than half of the youths. 

Levels varied by type but generally were higher among the Mohawk young adults than levels reported for a similar age group from the CDC’s national survey. For example, the total level of 13 specific PCBs in the Mohawk young adults was twice as high as levels reported in the CDC group. Many individuals had levels that placed them in the top 90 percent of the CDC’s measured levels.

Concentrations of nonpersistent PCBs were also higher in the Mohawk youths than the CDC report, possibly due to continued exposure to these shorter-lived varieties.

Elevated PCB levels were related to youths’ history and lifestyle. Higher persistent PCB concentrations were found in those born during or before the implementation of the 1984 fish consumption advisory. First borns, those who were breast-fed and those who ate local fish in the last year all had significantly higher levels of the total PCB varieties.

Prior studies find altered thyroid gland function and lower testosterone levels among the Akwesasne Mohawks.

What did they do?

Researchers collected blood from 152 Mohawk youths aged 17 to 20 years old (average of 18) who had participated in an earlier project, the Mohawk Adolescent Well-Being Study. They measured POPs chemicals in their blood, including 94 different PCBs plus p,p’-DDE and hexachlorobenzene (HCB). DDE is a breakdown product of the insecticide DDT, and HCB – used as fungicide until the mid-1960s – is a byproduct of chemical manufacturing.

HCB was also found in all of those sampled and p,p’-DDE in almost all. However, levels in the CDC youths were about five times higher for HCB and two times higher for p,p’-DDE. 

What does it mean?

Youths from the Mohawk Nation are contaminated with persistent organic pollutants at levels higher than the young adults studied in another national survey. Both past and current lifestyle factors – especially diet through eating fish and being breast-fed – influence exposure to and the concentrations of both the long-lived and less persistent POPs varieties in the Akwesasne Mohawk youth.

The data is consistent with past reports on POPs types and levels measured in the Akwesasne people.

In particular, elevated PCB levels were related to the youths’ history. Higher persistent PCB concentrations were found in those born during or before the 1984 fish consumption advisory began. And, those who ate fish in the last year had higher levels of the persistent kinds of PCBs. In contrast, higher levels of the less persistent varieties were measured in the participants who had not eaten fish recently.

The results also support prior breast-feeding studies that find birth order and duration influence contaminant transfer to the child. However, the study goes further and finds for the first time higher and longer sustained differences between breast-fed and non-breast-fed individuals.

Breast-feeding can be a major source of contaminant transfer from mother to child. Researchers found that breast-fed Mohawk youths – who stopped at an average age of 2.8 months, with the majority greater than six months – showed greater PCB contamination levels – about 1.3 to 1.5 times higher – than those not breast-fed. Further, the duration of breast-feeding was associated with total higher PCB levels measured in the young adults.

Prior studies show contaminant offloading through breast-feeding can be greatest with the first-born children. This research also finds that total PCB levels measured in Mohawk youths decreased from oldest to youngest. Taken together, these results support that persistent PCBs transferred during breast-feeding at least 17 years ago influence levels in the teenage Mohawk youths.

Even though, experts recommend nursing because of the health benefits to infants. Breast milk contains important components that boost immunity and supply important nutrients.

While the data add to a growing story about chronic exposure to long-lived pollutants, the results cannot be generalized to other populations.