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SAN JOAQUIN DELTA COLLEGE THRESHOLD LIMIT VALUES Toxics m m m3 mppcf Slight over 500 over 0 5 50 Moderate 101-500 0 101-05 20 High 0-100 0-01 2 TABLE III Threshold Limit Value - Short Term Exposure Limit (TLV-STEL) - The Concentration to which workers can be exposed continuously for a short period of time without suffering from 1) irritation, 2) chronic or irreversible tissue damage, or 3) narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency,and provided that the daily TLV-TWA is not exceeded It is not a separate independent exposure limit, rather it supplements the time-weighted average (TWA) limit where there are recognized acute effects from a substance whose toxic effects are primarily of a chronic nature STEL's are recommended only where toxic effects have been reported from high short-term exposures m either humans or animals The TLV's for gases and vapors are expressed in parts per million (ppm)which stands for parts of gases or vapors per million parts of air The TLV's for fumes, mists, and some dusts are given as milligrams per cubic meter (mg/m3) The TLV's of some dusts, i e, silica and asbestos, are expressed in millions of particles per cubic foot of air(mppcf) A STEL is defined as a 15-minute time-weighted average exposure which should not be exceeded at any time during a work day even if the eight hour time-weighted average is within the TLV Exposures at the STEL should not be longer than 15 minutes and should not be repeated more than four times per day There should be at least sixty minutes between successive exposures at the STEL Threshold Limit Value- Ceiling (TLV-C) -The concentration that should not be exceeded during any part of the working exposure Toxicology is the science of poisons, their effects on the body, various antidotes for their action, and their detection in body fluids and tissues See Table 1V for descriptive notations Since all chemicals can be toxic, it is necessary to define the conditions of an exposure as well as the amount of chemical involved in an exposure to compare toxicities(see Table V) NOTATIONS DESCRIPTIVE OF THE TOXICOLOGY Abbreviation Definition not limited to effects listed ALR Allergic systemic reaction such as might be experienced by individuals sensitized to penicillin BCM Blood clotting mechanism effects-any effect which increases or decreases clotting time BLD Blood effects - effect pm all b elements, electrolytes, pH, protein, oxygen carrying or releasing capacity BPR Blood pressure effects-any effect which increases or decreases any aspect of blood pressure _ . TABLE IV Page #4