hecked at least every three months to ensure adequate performance. System effectiveness should also be checked when there are any changes in production, process, or control that might result in significant increases in airborne exposure to these monohalomethanes.
If feasible, workers may be isolated from direct contact with the work environment by the use of automated equipment operated from a closed control booth or room. The control room should be maintained at a greater air pressure than that surrounding the process equipment so that air flows out of, rather than into, the room. This type of control will not protect workers who must perform process checks, adjustments, maintenance, assembly-line tasks, and related operations. Therefore, special precautions are often necessary to prevent or limit worker exposure in these situations and frequently involve the use of personal protective equipment.
Personal Protective Equipment
In a liquid state, all of the monohalomethanes discussed in this document may be injurious to both the skin and eyes upon direct contact. Liquefied methyl chloride and bromide are injurious to the skin because of rapid evaporation and the subsequent cooling effect which produces localized "burns" or "frostbite." Liquid methyl bromide has reportedly produced skin lesions and itching after skin contact and has resulted in conjunctivitis when accidentally splashed into the eyes.61 Other similar cases have been attributed to penetration of clothing by liquid methyl bromide.19,48,62
In one report on methyl iodide,29 it was noted that a soaked cloth pad applied to the forearm produced severe persistent lesions. These lesions were described as resembling those caused by mustard gas. These reports emphasize the importance of avoiding direct skin or eye contact with any liquid form of these monohalomethanes.29,63 This may be accomplished through the proper use of monohalomethane-resistant gloves, aprons, boots, or entire worksuits, depending on the nature and extent of the hazard. Faceshields or chemical safety goggles should be used wherever the potential for splashing exists.
The use of respiratory protection requires that a respiratory protection program be instituted which at a minimum meets the requirements of 29 CFR 1910.134.64 In addition to selection of respirators approved by the Mine Safety and Health Administration (MSHA) and NIOSH, a complete respiratory protection program should include at least regular training of personnel, maintenance, inspection, quantitative fit testing, and cleaning of equipment. The program should be evaluated regularly.
It must be stressed that the use of respiratory protection is the least preferred method of controlling worker exposures and should not be used as the only means of preventing or minimizing exposures during routine operations. However, NIOSH recognizes that respirators may be required to provide protection under certain situations (e.g., implementation of engineering controls, certain short-duration situations, emergencies, etc.). NIOSH maintains that only the most reliable respirators should be used to protect workers from exposure to workplace carcinogens. Such respirators consist of supplied-air, full facepiece, positive pressure respirators where odor warning and filter sorbent properties are not considered. Specifically, the following respirators are recommended for those situations.
- A self-contained breathing apparatus with a full facepiece operated in pressure-demand or other positive pressure mode or
- A combination respirator that includes a type C supplied-air respirator with a full facepiece operated in pressure-demand or other positive pressure or continuous flow mode and an auxiliary self-contained breathing apparatus operated in pressure-demand or other positive pressure mode.
A medical surveillance program should be available that can evaluate both the acute and chronic effects of exposure to these monohalomethanes. The physician responsible should be provided with an estimate of the worker's potential exposure to these monohalomethanes,