The Enviorment and you

Alarming Levels Of Mercury And Arsenic Found In Chinese Freshwater Ecosystem

The researchers studied three separate locations in Lake Baiyangdian, all at varying distances from major sources of pollution, such as coal emissions, agricultural runoff, and sewage discharge. They found concentrations of arsenic and mercury in fish were above the threshold considered by the U.S. Environmental Protection Agency (EPA) to pose a risk to humans and wildlife.

"It's important to study this system because it is typical of many throughout China where human activity and industrialization are having detrimental effects on the environment with major human health implications," says Celia Chen '78, a research associate professor of biological sciences. "It makes perfect sense to apply what we're learning about lakes in the U.S. to other places in the world, like China, that have a growing global impact."

Chen and her team were curious to learn how arsenic and mercury, two toxic environmental metals, moved through the food web in a freshwater ecosystem known to be polluted and contaminated. In a process called bioaccumulation, mercury and arsenic were found throughout the food web, from the water, into the algae, through the tiny algae-eating zooplankton, to the fish. As expected, the researchers found that more nutrient-rich environments supported larger algal blooms, which resulted in lower concentrations of mercury and arsenic in the water due to uptake by the algae.

In their previous work, the researchers found that when there is a lot of algae present, mercury and arsenic are biodiluted, or more dispersed, so zooplankton that eat the algae are exposed to lower levels of the metals and transfer less to fish.

"Despite this potential interaction - a decrease in bioaccumulation due to high algal biomass - the mercury and arsenic in this system are high enough to be of concern to humans and wildlife that drink the water and consume fish," says Chen. "For example, we saw arsenic levels in the water that represent more than fifty times the EPA-recommended limit for consumption of fish and shellfish."

Chen's co-authors include Carol Folt, dean of the faculty and professor of biological sciences at Dartmouth, Paul Pickhardt at Lakeland College, and M.Q. Xu at the Chinese Academy of Sciences in Beijing. Chen and Folt are both affiliated with Dartmouth's Center for Environmental Health Sciences and its Toxic Metals Research Program. Funding from the National Science Foundation and the National Institute of Environmental Health Sciences supported this work.

The findings were published online on Dec. 24, 2007, in the journal Water, Air, and Soil Pollution.

Air Pollution shrinks fetus sizes

Queensland University of Technology senior research fellow Dr Adrian Barnett said the study compared the foetus sizes of more than 15,000 ultrasound scans in Brisbane to air pollution levels within a 14km radius of the city.

"The study found that mothers with a higher exposure to air pollution had foetuses that were, on average, smaller in terms of abdominal circumference, head circumference and femur length," Dr Barnett said.

The 10-year study, which was undertaken by Dr Barnett, Dr Craig Hansen (US Environmental Protection Agency) and Dr Gary Pritchard (PacUser), has been published in the international journal Environmental Health Perspectives.

Dr Barnett, who is based at QUT's Institute of Health and Biomedical Innovation, said the study looked at foetuses between 13 and 26 weeks duration. "To our knowledge this is the first study of its kind as it uses ultrasound measurement as a direct estimate of growth, rather than using birth weight as a delayed measure of growth," Dr Barnett said.

"When analysing scans from women at different distances to monitoring sites, we found that there was a negative relationship between pollutants such as sulphur dioxide found in diesel emissions, and ultrasound measurement.

"If the pollution levels were high the size of the foetus decreased significantly."

Dr Barnett said with research showing that bigger babies were healthier in childhood and adulthood, foetus size during pregnancy was important. "Birth weight is a major predictor of later health, for example, bigger babies have been shown to have higher IQs in childhood and lower risk of cardiovascular disease in adulthood," he said.

"While some people may think there is no air pollution in Brisbane because the air looks so clean, you have to remember that most air pollutants are not visible to the naked eye, people do have a very outdoor lifestyle, and homes are designed to maximise airflow.

"So although the actual levels of pollution are low our exposure to whatever is out there is relatively high.

"This is particularly a problem for people who live near major roads."

Dr Barnett said it was wise for pregnant women to try to reduce their exposure to air pollution, most of which in Brisbane was caused by vehicles.

"While we need to get more data from individual mothers before we can be more certain about the effects of air pollution on fetal development, we would recommend that where possible pregnant women reduce their exposure to air pollution."