Researchers suggest that high levels of lead in the blood may double the risk of developing renal cell carcinoma in smokers.

Renal cell carcinoma is a form of kidney cancer that starts in the lining of small tubes in the kidney.

"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 in a released statement.

"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."

Renal cell carcinoma is the most common type of kidney cancer in adults, accounting for 92 percent of kidney cancers, according to the National Institutes of Health.

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.

The researcher’s analyzed data of nearly 30,000 Finnish male smokers between the ages of 50 and 69 years, enrolled from 1985 to 1988 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.

Penn State said in a statement that both Southard and colleague, Robin Taylor Wilson, associate professor of public health sciences at the College of Medicine, 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 wrote in the journal Cancer Epidemiology.

In support of past studies suggesting that higher calcium levels in the body can reduce lead retention, the authors found that among renal cancer cases alone, those with higher blood levels of calcium and vitamin D had a longer period of time before they developed cancer.

"This association suggests that vitamin D and calcium biomarkers may be important clues that can lead us to the early diagnosis of cancer," said Wilson.

The researchers said that this information is important because, currently, there are no screening tests for kidney cancer.

"Studies have shown that people with kidney cancer have higher average lead levels in their kidney tissue, compared with people without kidney cancer," said Southard.

"Prior to our study, this was only shown in cadavers and not in living people. Now we have shown that elevated blood lead levels put smokers at higher risk for renal cell carcinoma."