Are your halogens naked?

Two years ago, scientists at the University of Genoa in Italy reported in a letter to NATURE data indicating that ultraviolet light from tungsten halogen quartz lamps could induce skin lesions. Their findings came from three gene-toxicity tests and a carcinogenicity assay in 12 mice. Francesco D'Agostini and Silvio De Flora now update that report with data from five separate experiments involving 243 rodents. Their new work demonstrates the ability of halogen light to induce skin tumors in three strains of hairless mice.

All those exposed to the brightest light (10,000 lux) for 12 hours daily developed grossly deforming lesions within 8 months. However, benign and cancerous tumors occurred even with exposure conditions that emulated a 50-watt spotlight at a distance of 2 meters, De Flora and D'Agostini report in the Oct. 1 CANCER RESEARCH.

In contrast, the researchers failed to find any tumors in mice exposed to halogen lamps whose UV rays had been filtered out by inserting a plain glass cover over the bottom of the spotlight. Several nations already require such a glass cover for certain models of lamps, though its purpose is to protect consumers if the halogen lamp were to shatter.

The scientists say their findings "leave little doubt that uncovered halogen lamps may be potentially carcinogenic in humans." Frank R. de Gruijl of University Hospital Utrecht agrees, but notes that a colleague's rough calculations suggest long-term exposure to halogen's UV rays would only quadruple a Dutch citizen's lifetime risk of nonmelanoma skin cancer -- to perhaps about 4 chances in 100, well below the risk faced by Texas farmers who spend a lot of time in the sun.