Synergist - October 2009

considered a safer substitute for cigars and pipe tobacco, especially for bystanders; their weight control benefits could be touted for people who can’t tolerate cigars. Now imagine that the laboratory bioassay data that accumulated from the 1950s onward, including the Lovelace studies, were available for hazard evaluation. Would they carry the day in the current regulatory climate?

Experience suggests no. Claims that “high”—compared to prevailing—exposure levels in laboratory bioassays are suspect or irrelevant have undermined concerns for health risks to people at lower levels. For example, the observation that pigment-grade titanium dioxide caused lung cancer in rats was denigrated by the producers because the exposure level was 250 mg/m3. The “clearance overload” hypothesis was trotted out, as it was for silica. There was less complaint about the results of bioassays of ultra-fine titanium dioxide (about half of current nanotechnology by weight), which is more potent and causes increased cancer at lower gravimetric doses. Although IARC classified both size types as Group 2B carcinogens, possibly carcinogenic to humans, nothing has been done on the regulatory front.

Franklin Mirer, PhD, CIH, is a professor in the Environmental and Occupational Health Sciences Urban Public HealthProgramatHunterCollegeSchoolofHealthSciencesinNewYork.Hecanbereachedat(212)481-7651 orfmirer@hunter.cuny.edu.

References U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program: “Tobacco Related Exposures,” from Reporton Carcinogens, Eleventh Edition. Washington, D.C.: 2005. Online at http://ntp.niehs.nih.gov/ntp/ roc/eleventh/profiles/s176toba.pdf.

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