PRINCIPLES OF TOXICOLOGY - Biology East Borneo

524 CONTROLLING OCCUPATIONAL AND ENVIRONMENTAL HEALTH HAZARDS(1962), and labor unions began to lobby for better protective measures in workplaces. These eventsresulted in a number of legislative initiatives at the end of the decade. Along with other environmentallaws, the Occupational Safety and Health Act (OSHA) was passed in 1970. The OSHAct assured thatevery employee “has the right to a workplace free of recognized hazards.” Since that time, the fieldof industrial hygiene has grown dramatically, both in size and sophistication.The basic philosophies of industrial hygiene are well-recognized: protection of worker health is aworthwhile goal; the burden of protecting the worker is primarily the employer’s, but the worker alsohas the responsibility to exercise self-protection. The hierarchy of control measures is, in order ofeffectiveness, elimination of toxic chemical use, substitution of less toxic material for more toxicsubstances, engineering controls, administrative controls, and personal protective equipment. Educationand training of workers is increasingly recognized as a key aspect of industrial hygiene, asevidenced by the proliferation of “right to know” laws that have swept the country. Essentially, theidea is that an informed worker is a safer worker; if employees understand why a safety rule has beenestablished, they are more likely to follow it.The control of occupational health hazards is dependent on the anticipation of potential healthhazards in new facilities and their recognition in existing facilities. Once the potential health hazardshave been identified, they are evaluated by a process of observation of the work place and workpractices and quantification of the risk associated with the hazard. When these risks reach unacceptablelevels, methods of controlling the exposures must be identified and implemented to minimize thepotential for harm to the worker. The identification and evaluation phases are sometimes referred toas risk assessment, while the control phase is referred to as risk reduction or risk management.In practice, the industrial hygienist plays the major role in the risk assessment process. On the otherhand, risk reduction involves many different players with a variety of backgrounds: the supervisorsand workers who know the process and must work with any new equipment or procedures that areinstalled; engineers who are familiar with control technologies and understand the production process;toxicologists who may identify adverse effects from chemical exposure; physicians capable ofdesigning medical surveillance programs to help identify emerging adverse health effects in individuals;the industrial hygienist who understands how contaminants behave in both the environment andthe human body and understands when to use the various control strategies; and managers who mustallocate sufficient resources to pay for controls. Each player brings special abilities and knowledge tothe problems associated with minimizing health risk.As an applied science, industrial hygiene relies on the basic sciences of biology, chemistry, physics,and statistics, as well as the social sciences—sociology, and political science—to achieve its goals.22.2 EXPOSURE LIMITSThe bridge between toxicology and industrial hygiene has traditionally been the development ofexposure limits. Exposure limits are reference values that should not be exceeded. They have beendeveloped to protect the large majority of an exposed population from the development of environmentallyinduced diseases. The level of protection varies with the type and severity of the expectedoutcome as well as the sensitivity of the exposed population.Air-Contaminant Exposure LimitsThe threshold limit values (TLVs ® ) for chemical substances have been published by the AmericanConference of Industrial Hygienists (ACGIH) since 1946 and have increased in number since thattime. Generally, the TLVs ® for many substances have been lowered as the identification of more subtleadverse health effects has become possible. Mastromatteo (1988) documented the history and progressionof TLVs ® . ACGIH bases the TLVs ® on information gathered by the ACGIH TLV ® Committeefrom human experience in the workplace and experimental human and animal studies.