INDUSTRIAL-HYGIENE ASPECTS OF A SAMPLING SURVEY AT A BLEACHED KRAFT PULP-MILL IN BRITISH-COLUMBIA

To validate exposure estimates used to investigate correlations betwee n exposure and cancer risk, 1678 personal measurements were collected for 46 job titles during 73 day shifts at a bleached-kraft pulp mill. Measurements included shift-long average and short-term exposures to c arbon monoxide, chlorine dioxide (ClO2), and hydrogen sulfide; and shi ft-long average exposures to calcium oxide and wood dust (WD). Overall results indicate low levels of exposure with a few noteworthy excepti ons. Although ClO2 was the exclusive bleaching agent, 77 area samples indicated that chlorine (Cl-2), not ClO2 was present in all areas apar t from the chemical preparation area (chem-prep) and during a pulp spi ll. The highest shift-long exposures to Cl-2 were measured in the chip yard and are attributed to uncontrolled stack emissions. Finally, WD samples collected from several laborers significantly exceeded regulat ory limits, with the highest exposures measured in the steam and recov ery area. For short-term exposures to ClO2 in chem-prep, 12 of 17 data -logging electro-chemical sensor sample results showed at least one pe ak that exceeded the short-term exposure limit of 0.3 ppm. The use of data-logging equipment quantified short-term exposures that previously had been characterized only anecdotally. The peaks were correlated wi th tasks and upset conditions and, given their transient nature, these exceedances could not have been detected using shift-long average-bas ed sampling devices. Since the respiratory effects of significant shor t-term exposures to irritant gases such as Cl-2 and ClO2 are well-docu mented, data-logging instruments are necessary to characterize exposur es in the pulp and paper industry.