Methods to control styrene exposure in the reinforced plastics industry

Currently, about 75% of Finnish reinforced polyester lamination workers are exposed to styrene concentrations exceeding the current occupational exposure limit of 20 ppm. Several measures have been proposed to control styrene exposure, but only a few of them are capable of keeping the styrene concentration below 20 ppm. The present study was carried out to evaluate current ventilation systems in reinforced plastic plants and to develop new, effective ventilation systems for controlling styrene exposure. The roles of styrene-suppressed resin and styrene emission during different phases of the moulding process were also studied. Styrene exposure and the performance of current ventilation systems were measured in 17 reinforced plastics plants. Better styrene control was sought experimentally by investigating the effects of unidirectional airflow on a worker’s exposure, by testing local exhaust and local air supply ventilation methods in controlling laminator’s exposure and by examining the possibilities to improve local ventilation using an automatically moving ventilation unit. The characteristics of styrene emission during hand lay-up and the effect of a rolled area on styrene evaporation were also determined. Dilution ventilation systems are common in Finnish reinforced plastics plants. In many cases, the ventilation system was incorrectly dimensioned and workers were exposed to high styrene concentrations. High dilution airflow rates, over 850 m kg, may be needed before a concentration level below 20 ppm is achieved with the resin consumption rates common today. In order to meet the present exposure limit, local ventilation techniques should be used in combination with other control measures.