Styrene exposure within the Swedish reinforced plastics industries 1970-2010

Introduction
Styrene is used in the reinforced plastics industry (AP industry) and is classified as a carcinogen group 2B by IARC (International Agency for Research of Cancer). Person-borne exposure measurements of styrene have been conducted on a larger scale in Sweden since 1970. These measurement reports are stored by the Swedish Work Environment Authority (AV). Large technical improvements over the years have been taken to reduce exposure. The purpose of this study is to study the exposure pattern in the AP industry between 1970 and 2010.

Methods
Multi-day measurements of air concentrations of styrene have been systematically implemented in the AV studies within the AP industry in years 1970-72, 1987-89, 1997 and 2009, and are now systematically undertaken. Samples have been person-borne and workplaces in each measurement exercise selected to be representative for the Swedish AP industry as plastic boat manufacturing industry (large- and small scale), large plastic tanks, cisterns, general plastic manufacturing. At each study has about 100 full shift styrene averages determined at almost 25 similar worksites. The number of exceeds of the Occupational Exposure Limits (OEL) were recorded and the average styrene exposure levels for the total AP industry were calculated. All measurements have been related to Swedish OEL (2004) for styrene (90 mg/m3).

Results
95% of the full shift samples (n = 125) exceeded the OEL in years 1970-72 with mean 515 mg/m3. In 1987-89 exceeded 42 % the OEL while 15% of the samples with mean 49 mg/m3 in 1997. The year 2009 exceeded 28% of all measurements OEL with mean 50 mg/m3. For the corresponding measurements inside the respirator (face mask) in 2009, the mean exposure level was 6 mg/m3.

Discussion
Technical improvements have substantially reduced styrene exposure during the 1970's and 1980's. The last 10 years, the exposure levels have remained unchanged.