PRINCIPLES OF TOXICOLOGY - Biology East Borneo

22.4 CASE STUDIES 541• Physical assessment and fit testing of affected employees• Employee training in proper use and limitations of respirators• Respirator storage• Respirator inspection, cleaning and disinfection, and replacement as needed• Regular inspection and monitoring/surveillance of work area conditions and employeeexposure and stress• Periodic program evaluationTo effectively administer a comprehensive program requires a substantial amount of time, technicalcompetence, and money. Some program elements are a major concern, such as respirator fit and medicalevaluation. Respirator manufacturers began producing multiple-size facepieces available and softrubber facepieces only in the late 1990s to accommodate the variety of sizes and facial shapes.Respirators must be fitted to each individual either in quantitative or qualitative tests, which have usedestablished protocols involving the use of challenge agents such as corn oil or irritant smoke. Finally,some individuals are unable to wear respirators at all, because of facial shape or a preexisting medicalproblem, such as dentures or heart disease. A particularly sticky concern associated with wearingrespirators is that there are no definitive medical tests, which can lead a physician to determine whethera worker can wear a respirator without suffering adverse health effects.In spite of all these limitations, respirators have saved many lives. They must be used when otherfeasible methods of control have been exhausted. And of course they are basic to emergency responseprocedures where there is no time to use other controls, or when one is facing an unknown situationthat requires immediate action.The same basic principles apply to other forms of personal protection: they all increase the stressburden on workers, but with proper training, they can form an effective barrier between the toxicsubstance and the body. For example, protective clothing can cause heat stress unless employees areprovided with additional breaks and water intake. Face shields can protect the eyes and face fromcorrosive substances, but also reduce visibility. Gloves protect the hands, but at the cost of reduceddexterity. Hardhats and steel-toed shoes provide protection from safety hazards, but also add weightthat the worker must carry around during the workshift.All forms of personal protection require expert selection. The correct respirator cartridge must beused for the particular chemical, concentration, and physical state. For example, a dust filter willprovide no protection against gases or vapors. Protective clothing that is not impermeable to thechemical can actually worsen skin exposure by providing a continuous reservoir of unevaporated liquiddirectly in contact with the skin. Guidance in the selection of appropriate protective equipment maybe available on the MSDSs. Other sources include the NIOSH Pocket Guide to Chemical Hazards andGuidelines for the Selection of Chemical Protective Clothing.Summary of Control Technologies In any given situation, it is unlikely that any single specificcontrol technique will prevent exposures to toxic substances. The challenge in occupational hygieneis to arrive at a logical blend of all the alternatives outlined above to provide a workplace free ofrecognized health hazards and at least a good head start on those occupational health hazards we haveyet to discover.22.4 CASE STUDIESHerbicide Application in the ForestThe first case study involves the exposure of herbicide applicators in the management of forests. Thisexample demonstrates the bridge between industrial hygiene and toxicology. It also demonstrates that