Exposure of contractors to chemical pollutants during the maintenance shut-down of a chemical plant

The exposure of employees of different contracting firms to chemical pollutants was assessed during the five-week biennial maintenance shut-down of an isocyanate (TDI) synthesis plant. This assessment was mainly based on personal sampling, but work-related constraints occasionally required that area samples be used instead. Many tasks were carried out during the shut-down procedure (dismantling of reactors, installation of insulation, refection of kilns, cleaning, painting, electricity, etc.), thereby causing the employees of the contracting firms to be exposed to different kinds of pollutants, including products used or manufactured in the process (solvents, TDI and its synthesis intermediates), and products specific to the contractors' activity (welding fumes, crystalline silica, mineral fibers of heat insulation). The highest level of exposure (mainly to TDI) was found for the mechanical engineering activities undertaken during the dismantling of reactors and for cleaning activities. It was demonstrated that there was much variability in day-to-day exposure levels, and occasionally in the exposure levels encountered during a given shift. Cases of concomitant exposure to TDI (mainly short-term exposures) and other pollutants due to simultaneous activities from different tasks in the same area (co-activity) were also observed. Both the need for, and limitations of personal protective equipment (mainly respiratory) are stressed. Special emphasis is put on the responsibility of the owner of the facilities in helping the contractors in the organization of a health and safety policy.