Linking Toenail Arsenic Content to Cutaneous Melanoma

Laura E. Beane Freeman, Ph.D., National Cancer Institute
and Peter S. Thorne, Ph.D., University of Iowa
T32ES07314 (support for Dr. Beane Freeman) and P30ES05605

Background: Cutaneous malignant melanoma incidence is increasing the U.S. and its annual percentage increase is one of the highest for all cancers. This deadly cancer has the lowest survival rate of all skin cancers. Approximately 54,200 cases were diagnosed and 7,600 deaths were attributed to cutaneous melanoma in the U.S. in 2003 alone.

Although exposure to the metalloid element arsenic has been associated with other forms of skin cancer and vascular diseases, little research has been conducted on possible links between arsenic and cutaneous melanoma. These NIEHS-supported investigators performed what may be the first epidemiologic study to investigate the association between cutaneous melanoma and environmental arsenic exposure in 741 Iowans age 40 and over.

Advance: The study participants completed a survey and submitted toenail clippings for arsenic analysis. The researchers found about a two-fold increased risk of melanoma for participants with elevated toenail arsenic concentrations. Risk of melanoma with increasing toenail arsenic content was almost seven times greater for those with a prior skin cancer diagnosis. Participants with the highest toenail arsenic levels were more likely to use private wells as compared to those with the lowest arsenic levels. Private well use is a known risk factor for arsenic exposure.

Implications: These findings are important because of the potential for large numbers of people to be exposed to arsenic world-wide. The higher observed effect in people with prior skin cancer diagnosis lends further support to a causal association between arsenic and cutaneous melanoma. The authors speculate that this finding may not have been previously reported because similar studies have been conducted primarily in Asian populations where risk of melanoma is much lower than in Caucausian people. Darker skin color may modify the effect of arsenic on melanoma risk. Further research needs to be conducted to confirm these results and further investigate the link between arsenic exposure and development of melanoma.

Citation: Beane Freeman LE, Dennis LK, Lynch CF, Thorne PS, and Just CL. Toenail arsenic content and cutaneous melanoma in Iowa. American Journal of Epidemiology; 160(7); 679-87.