Lead blood levels may increase smokers' risk for kidney cancer

Higher than normal levels of lead in the blood may signal a risk two times higher than average of developing renal cell carcinoma in smokers, according to medical researchers.

"Past studies (in cadavers) have shown that, compared with kidneys from individuals without cancer, kidneys from individuals with cancer have higher lead levels," said Emily B. Southard, medical student at Penn State College of Medicine. "But prior to this study, the identification of higher lead in blood as a risk factor among healthy individuals before they develop kidney cancer had not been shown."

Southard, working with Robin Taylor Wilson, associate professor of public health sciences at the College of Medicine, analyzed data collected from the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study to measure levels of blood lead, calcium and vitamin D in stored blood donated by healthy individuals several years before renal cell carcinoma ever developed.

According to the National Institutes of Health, renal cell carcinoma is the most common type of kidney cancer in adults, accounting for 92 percent of kidney cancers. The National Cancer Institute of the NIH predicted that there would be about 56,000 new cases of RCC in 2011 and has reported that nearly 300,000 people in the United States are living with kidney cancer today.

In previous studies involving animals, researchers had found an inverse correlation between the amount of lead retained in the body and the amount of calcium in the diet. This supports the hypothesis that higher calcium levels in the body can reduce lead retention. While Southard and Wilson also found that levels of calcium were higher in men who had a lower risk of kidney cancer, there was not a strong correlation between blood levels of lead and blood level of calcium or 25-hyrdoxyvitamin D. Therefore, they could not conclude that calcium or vitamin D levels had an influence on the risk observed related to blood lead levels.

Southard and Wilson looked at whether the subjects had ever been in a "high-risk occupation," which would expose the subject to more lead than an average person - such as mining, asbestos fabric manufacture or oil refining.

"There were no significant differences in occupational history or smoking history between cases and controls in our study that would sufficiently explain the association we observed," the researchers reported online in Cancer Epidemiology, Biomarkers and Prevention.

Pulling together data from 24 studies conducted since the 1960s, an international research team found that the risk of kidney cancer was 38 percent higher among people who had ever smoked versus those who had never picked up the habit.

And the more smokers had puffed over a lifetime, the greater the risk to their kidneys — a so-called dose-response relationship that supports a direct link between smoking and kidney cancer.