Investigating Environmental Health Risks – Module Issues in the News for Students
Even Low Levels of Lead Affect IQ
It has been known for a long time that exposure to lead lowers IQ (intelligence quotient). It was widely held that 10 micrograms of lead per deciliter of blood or more could affect a child’s development. A five-year study sponsored by the National Institute of Health now suggests that much lower lead levels can affect IQ.
The study focused on 172 children in Rochester, New York. The amount of lead in their blood was measured at 6, 12, 18, 24, 36, 48, and 60 months, and they took IQ tests at ages 3 and 5. Other variables that affect IQ, such as birth weight, income, education, and amount of stimulation in the home, were controlled. “In this sample of children we find that most of the damage to intellectual functioning occurs at blood lead concentrations that are below 10 micrograms per deciliter,” said Richard Canfield of Cornell University and the primary author of the study.
The study concluded there was no safe threshold for lead exposure.
Does a Healthy Diet Poses a Different Set of Risks?
Greenland’s native population, the Intuits, has very few cases of heart disease, diabetes, and obesity. This is tied to their diet, which consists of polar bears, seals and, whales. Recently however, scientists have discovered the Intuits have “unacceptable levels” of environmental toxins, including mercury, lead, cadmium, and persistent organic pollutants (POPs). These toxins can lead to health effects such as reduced fertility, genetic damage, and deformities in children.
These toxins are not found on Greenland, so how did the Intuits get exposed to these toxins? They are carried north by sea currents and weather patterns. Polar bears, seals, and whales are exposed to the pollutants in the environment. The toxins bioaccumulate and move up the food chain to humans.
More Beach Pollution or Flawed Sampling Methods?
In 2001, 19% more beaches were closed because of contaminated water than in 2002. But experts say the water is cleaner than before. So why are the beaches being closed? Scientists at the University of California at Irvine say it is because of the way the water is being tested.
Scientists studied 43 years of water quality data at Huntington Beach, California, and determined the water is cleaner now than it has ever been. Water quality depends on many factors, such as tidal cycles, seasonal rainfall, and El Nino events. They theorize that the increased number of closures is because there is now more beach monitoring and a lower acceptable limit for levels of bacterial contamination.
The way the water is sampled is also in question. Beach closings are determined by the results of a single water sample. Experts say that water quality changes quickly, and that one sample does not give a true picture of overall water quality. Instead, they recommend a method that averages the results of multiple samples from a single beach before a decision is made.