In several countries, dental personnel had higher mercury levels in biological fluids and tissues than in control groups; some work practices increased mercury exposure but the exposure levels remained below recommended guidelines.
With one exception, the results showed the exposure levels were well below the OSHA permissable exposure levels and recommended American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values.
The minuscule (parts per billion) levels are well below the safe exposure level set in the 1980s by the Environmental Protection Agency EPAA).
Such O3 concentrations are lower than the U.S. ambient air quality standards for O3, which are an 8-hr average at 80 ppb and a 1-hr maximum at 120 ppb, and below the permissible exposure level for workers promulgated by the U.S. Occupational Safety and Health Administration (2004), which is an 8-hr time-weighted average of 100 ppb.
Microarray technology for the global analysis of gene expression may be a sensitive enough tool to address the low end of the dose-response curve down to and below ambient exposure levels, thereby providing a basis for establishing pragmatic thresholds.
The probing power was 42 μW, which is well below the safe occupational exposure level established by the American National Standards Institute (ANSI Z 136.1).
For categorized cumulative and average exposures to DCE and vinyl chloride, as well as average exposure to PCE, the exposure-response relationships were not monotonic since the adjusted ORs at the low exposure level were below 1.00.
Using the low-dose threshold models with a flat dose response below the lowest observed exposure levels, the BMDL results for the linear curve were about 5-fold higher than for the non-threshold curve (Table 3).
Regulating to achieve a purported beneficial response would require standards to be set at a specified level rather than below an exposure level.
The main reasoning was as follows (Nielsen and Wolkoff 2010; Wolkoff and Nielsen 2010): (1) Epidemiological studies reported no increased incidence of nasopharyngeal cancer in humans below a mean exposure level of 1 ppm and peak levels below 4 ppm, consistent with results from rat studies.
