Introduction Styrene is genotoxic, an animal carcinogen, associated with lymphohematopoietic malignancies in humans, and classified as a group 2A carcinogen by the IARC.

Objective To combine and harmonize existing cohorts of reinforced plastics industry workers with the aim to study exposure-response relations for styrene and subtypes of lymphohematopoietic and other malignancies as well as non-malignant diseases.

Methods Six European cohorts included in an earlier IARC coordinated cohort and one US cohort participated. They all have been previously used in investigation of the health risks of styrene exposure. They will be updated with extended follow-up until 2019–2020 in national registries for mortality and cancer incidence. Personal air styrene measurements and biological markers of styrene exposure from the 1960s up to the present day will be used to update the exposure assessment. Linear mixed-effects models will be applied to develop a quantitative, historical, industry-specific job-exposure matrix. Predictors available in the individual cohorts include country, occupation, employment year, product, process, and task. Some cohorts will be pooled together prior to analysis, others analyzed separately following a common protocol that will focus on different exposure metrics (cumulative, duration, mean, highest attained, peaks) and exposure time windows. The aggregated data will be synthesized by a meta-analysis.

Results A total of 96,000 workers employed between 1947–2007 in 762 companies in Finland, Italy, UK, US, and Denmark, and over 2.8 million person years will be included, and 40,000 air samples and 13,000 urinary samples are identified.

Conclusion Pooling and meta-analysis of existing cohorts are powerful tools in the search for more definite answers to the carcinogenicity of this important chemical.