Children who are exposed to high levels of arsenic in their drinking water are seven to 12 times more likely to die of lung cancer and other lung diseases in young adulthood, a new study by University of California, Berkeley, and Chilean researchers suggests.
The risk of dying due to bronchiectasis, usually a rare lung disease, is 46 times higher than normal if the child's mother also drank the arsenic-contaminated water while pregnant, according to the study. These findings provide some of the first human evidence that fetal or early childhood exposure to any toxic substance can result in markedly increased disease rates in adults.
"The extraordinary risk we found for in utero and early childhood exposure is a new scientific finding," says the study's lead author, Allan Smith, professor of epidemiology at UC Berkeley's School of Public Health. "I sometimes ponder the improbability that drinking water with concentrations of arsenic less than one-thousandth of a gram per liter could do this, and think that I've got to be wrong. But our years of working with arsenic exposure in India and Chile tie in with this study perfectly."
The paper appears in Environmental Health Perspectives.
Classified as a semi-metal, the element arsenic is one of the most potent cancer-causing agents known. Skin, bladder and lung cancer rates are substantially higher in regions where the tasteless, colorless substance occurs in drinking water. A recent study by Smith showed that adults exposed to arsenic can also develop decreased lung function similar to that experienced by cigarette smokers. And, in a paper published in the American Journal of Epidemiology, Smith and his colleagues provide evidence that women exposed to high concentrations of arsenic during pregnancy experience six-fold increases in stillbirths and other adverse effects.
Arsenic is particularly prevalent in Region II, a province in the north of Chile and one of the driest places on earth. In 1958, the cities there of Antofagasta and neighboring Mejillones tapped into arsenic-laden rivers to supply their growing populations with water. For the next 13 years, until an expensive arsenic removal plant was installed, the water supply for all residents in the cities was laced with an average of 860 micrograms per liter of arsenic. In contrast, the standard for arsenic in drinking water in the United States was recently dropped from 50 micrograms per liter to 10 micrograms per liter, with compliance required in 2006. (A microgram is a millionth of a gram.)
With such clear-cut exposure to arsenic, the unfortunate Chilean cities became a tragic natural experiment for studying the effects of arsenic on humans.
From earlier work he and others conducted in India, Smith knew that arsenic is associated with bronchiectasis, a rare lung disease that causes distortion and dilation of the bronchi, eventually leading to chronic infections. A study involving death certificates for young adults in Antofagasta and Mejillones, Smith realized, would reveal whether lung cancer and bronchiectasis could also occur as a result of childhood exposure to arsenic. Working with colleagues Guillermo Marshall and Catterina Ferreccio from the Pontificia Universidad Catslica de Chile in Santiago, Smith compared the death rates from 1989 to 2000 of young adults in the two cities with the rates in the rest of Chile, outside of Region II. The team focused on two groups: those born between 1951 and 1958, when the water supply to the cities had relatively low arsenic concentrations, and those born during the high-exposure period of 1958 to 1971.