No abstract

This article recommends an 8-hour occupational exposure limit (OEL) for beryllium. It responds to growing concerns about the continuing incidence of chronic beryllium disease despite the long-standing OEL for beryllium: 2 micrograms of beryllium per cubic meter of air (microgram/m3), 8-hour time-weighted average (TWA). Current 8-hour TWA beryllium OELs are not based on chronic beryllium disease toxicology and an increasing number of studies report incidence of chronic beryllium disease at exposure levels apparently below 2 micrograms/m3. The experience of the beryllium-exposed population of Lorain, Ohio, in the late 1940s, and the ambient air regulatory standards derived from that event provide evidence that establishing a protective level is possible. These levels are used as the basis for a new recommended beryllium exposure standard. A correspondingly protective 8-hour TWA level of 0.1 microgram/m3 has been derived, which, for commonly encountered workplace conditions (in terms of geometric standard deviation and percent-compliance), should provide long-term mean exposure protection comparable to that received by the unaffected Lorain subpopulation and provided by the Environmental Protection Agency (EPA) ambient standard. It is concluded that an exposure limit of 0.1 microgram/m3 combined with exposure monitoring to assure a high rate of day-to-day compliance would provide better control of both long-term mean exposure levels and short-term levels than do current occupational exposure limits. The health data available, while certainly not conclusive, support further reductions in exposure levels to help minimize the incidence of chronic beryllium disease.

No abstract

The purpose of this study was to investigate the relationship between the American Conference of Governmental Industrial Hygienists' (ACGIH) time-weighted average (TLV-TWA) and short-term exposure limit (TLV-STEL) Threshold Limit Values (TLVs). It is of value to determine if one or the other of these exposure limits is inherently more stringent so that exposure monitoring strategies may be devised which efficiently use available resources and effectively control exposures to meet both exposure limits. The ACGIH short-term exposure limit (TLV-STEL) imposes three conditions on short-term (15-minute) exposures. These conditions involve exceeding the TLV-TWA and TLV-STEL levels and the time-separation of those short-term exposures that exceed the TLV-TWA level. These conditions were analyzed to produce eight unique component probabilities for TLV-STEL non-compliance. The sum of these eight components is the total probability of TLV-STEL non-compliance. Mathematical expressions for the eight probability components are derived in terms of the probability that a single 15-minute exposure exceeds the time-weighted average threshold limit value (TLV-TWA) and the geometric standard deviation of these 15-minute exposures. These expressions were applied to various hypothetical workplaces, and the relationship between TLV-TWA and TLV-STEL compliance is presented. The results showed that non-compliance of 15-minute exposures with the TLV-STEL level is only one part of overall TLV-STEL non-compliance. The additional ACGIH provisions for TLV-STEL compliance--the number of 15-minute exposures exceeding the TLV-TWA level and the number of clean periods separating such exposures--can be important factors in determining TLV-STEL compliance. It is concluded that compliance with all provisions of the ACGIH TLV-STEL adds a degree of stringency that greatly enhances the likelihood of TLV-TWA compliance for most workplace environments.

No abstract