The MAK Collection for Occupational Health and Safety now is available on-line and free. It provides the German recommended exposure limits with documentation for chemicals used in Germany and many other countries. The MAK-values are daily 8-hour time-weighed average values and apply to healthy adults. Substance-specific acceptable peak concentrations, including the highest possible duration of such peaks, [...]
Below is a summary of some of the very similar methods and rationale used by agencies to assess the combined toxic effects of chemicals.
ACGIH Source: TLV’s and BEI’s Publication
Recommends an additive (combined) approach for two or more substances that affect the same target organ/system The ratio of the exposure concentrations are summed together [...]
OSHA currently has two standards in which the PEL is adjusted based on the length of the work shift, both of which are lead standards:
29 CFR 1910.1025 29 CFR 1926.62
All other PELs are based upon 8-hour time weighted average (TWA), a short term exposure limit (STEL), or a ceiling limit (C).
The lead [...]
The purpose of this memorandum is to resolve issues concerning adjustments of the PEL during extended work shifts. This applies for exposures to the noise levels of Table G-16 of 29 CFR 1910.95 or substances found in Subpart Z. Current OSHA policy requires only the action level to be reduced for exposures to noise during [...]