Evaluation of half-mask respirator protection in styrene-exposed workers.
OBJECTIVE
The protection afforded by respirators to styrene (St)-exposed workers varies considerably. Our objective was to study the effective 'in the field' reduction in St exposure obtained by negative-pressure half-mask respirators worn by a group of fiberglass-reinforced plastics (FRP) workers. Protection was evaluated by measuring the reduction in urinary St (StU) excretion.


METHODS
Seven FRP workers not using respiratory protection devices were studied for a week. External exposure to St was evaluated by personal passive sampling, and the internal dose by StU measurement. Then workers were asked to use a half-mask respirator for a week for the entire morning half-shift, and St exposure and internal dose were re-assessed.


RESULTS
Mean environmental levels of St during the morning half-shift were 230-280 mg/m3, i.e., about three times the current limit proposed by ACGIH; the difference among days was not significant. Using respirators was accompanied by a large inter-individual and also intra-individual variability: the estimated reduction of StU values ranged from 30% to 90% (mean 60%). Mean StU values increased by 50% from Monday to Friday, while environmental St concentrations remained steady. Furthermore, the proportion of workers exceeding the biological equivalent exposure limit (BEEL) was 14% on Monday, double (33%) on Thursday, and triple (43%) on Friday. These data suggest a decrease of protection during the week.


CONCLUSIONS
The protection afforded by negative-pressure half-mask respirators varies widely, which stresses the need to assess the effective reduction of exposure whenever these devices are introduced for St-exposed workers. If respirators are to be re-used for several days, their performance must be evaluated during the last shift of use. Measurement of urinary excretion of unmodified St proved a useful tool for the evaluation of respirator effectiveness in exposed workers.
Gobba
F
F
Dipartimento di Scienze Igienistiche, Microbiologiche e Biostatistiche Università di Modena e Reggio Emilia, Italy. gobba@unimo.it
Ghittori
S
S
Imbriani
M
M
Cavalleri
A
A
D000395:Air Pollutants, Occupational / Q000506:poisoning*; D006801:Humans; D008397:Masks; D016273:Occupational Exposure; D010969:Plastics; D011041:Poisoning / Q000517:prevention & control; D012134:Respiratory Protective Devices; D020058:Styrene / Q000506:poisoning* / Q000652:urine
D000395:Air Pollutants, Occupational; D010969:Plastics; D020058:Styrene