Lanska D J
Veteran Affairs Medical Center, Great Lakes Health Care System, Tomah, Wisconsin 54660, USA.
J Public Health Policy. 1999;20(4):441-58.
Available industry guidelines and federal standards have failed to fully protect workers from chemical toxicity: none exist for most chemicals, many are biased toward what can easily be achieved, and many were developed long after health consequences became evident. Limitations of occupational air contaminant standards in the United States are well illustrated by standard-setting for the neurotoxin n-hexane. In the 1940s, the American Conference of Governmental Industrial Hygienists (ACGIH) first promulgated industrial guidelines known as "threshold limit values" (TLVs), including an 8-hour time-weighted average of 500 ppm for inspired n-hexane. Despite subsequent recognition of the neurotoxicity of n-hexane with industrial outbreaks of polyneuropathy beginning in the 1960s, the TLV for n-hexane remained unchanged until 1976 when a value of 100 ppm was adopted. Because a growing number of clinical reports have identified clinical and subclinical neurotoxicity from n-hexane near, at, and below the current time-weighted average TLV of 50 ppm, even this level is too high to protect all workers. In part due to procedural and political constraints, the Occupational Safety and Health Administration (OSHA) has independently developed only a small number of exposure standards in the past 25 years, and has been incapable of providing needed revisions for existing standards. Most OSHA standards--including those for n-hexane--were adopted in 1971 from the 1968 ACGIH TLVs and have never been revised. From 1971 to 1989 the OSHA permissible exposure level (PEL) for n-hexane remained at 500 ppm, 5-10 times as great as other contemporary standards. To help correct its regulatory backlong, OSHA promulgated 375 new or revised PELs in 1989--including a new standard of 50 ppm for n-hexane--but all of these were vacated by the 11th U.S. Court of Appeals in 1992. As a result, the current OSHA PEL for n-hexane remains at the 500 ppm level adopted in 1971, which even then was too high based upon available scientific evidence. New information over this long period, including that obtained from industrial outbreaks of disease due to chemical exposures, has not been incorporated into revised federal standards.
大多数化学品没有相关标准，许多标准偏向于易于实现的目标，而且许多标准是在健康后果显现很久之后才制定的。美国职业空气污染物标准的局限性在神经毒素正己烷的标准制定中得到了充分体现。20世纪40年代，美国政府工业卫生学家会议（ACGIH）首次颁布了名为“阈限值”（TLVs）的行业指南，其中规定吸入正己烷的8小时时间加权平均值为500 ppm。尽管自20世纪60年代正己烷引发工业性多发性神经病疫情后，人们随后认识到了正己烷的神经毒性，但正己烷的阈限值直到1976年才被修订为100 ppm。由于越来越多的临床报告表明，在当前50 ppm的时间加权平均阈限值附近、达到该值及低于该值时，正己烷都会导致临床和亚临床神经毒性，所以即使是这个水平也过高，无法保护所有工人。部分由于程序和政治方面的限制，职业安全与健康管理局（OSHA）在过去25年里仅独立制定了少数接触标准，并且无法对现有标准进行必要的修订。大多数OSHA标准——包括正己烷的标准——于1971年采用了1968年ACGIH的阈限值，此后从未修订。1971年至1989年，OSHA对正己烷的允许接触水平（PEL）一直保持在500 ppm，是其他同时期标准的5至10倍。为了纠正其监管滞后的问题，OSHA在1989年颁布了375项新的或修订后的PEL——包括正己烷的新标准50 ppm——但所有这些标准在1992年被美国第十一巡回上诉法院撤销。结果，OSHA目前对正己烷的PEL仍维持在1971年采用的500 ppm水平，而即便在当时，根据现有科学证据，这个水平也过高了。在这么长的时间里出现的新信息，包括从化学品接触引发的工业疾病疫情中获得的信息，都没有被纳入修订后的联邦标准中。
