Table 3.

Adjusted incidence rate ratios with 95% CI for seropositive* and seronegative† rheumatoid arthritis by cumulated styrene exposure level in 59 997 male and 12 215 female workers in the Danish reinforced plastics industry, 1979 to 2012

Styrene exposure level	Rate ratio‡ seropositive				Rate ratio‡ seronegative
	n	Men	n	Women	n	Men	n	Women
	156		60		157		84
≤17 mg/m3 years		1		1		1		1
18–67 mg/m3-years		1.19 (0.79 to 1.81)		0.89 (0.45 to 1.76)		1.17 (0.75 to 1.83)		0.97 (0.59 to 1.58)
≥68 mg/m3‡-years		1.11 (0.73 to 1.70)		1.95 (1.05 to 6.61)		1.52 (0.99 to 2.34)		0.49 (0.24 to 0.98)
Per 100 mg/m3-years		0.98 (0.93 to 1.04)		1.11 (1.01 to 1.22)		1.04 (1.02 to 1.07)		0.87 (0.70 to 1.09)

*Seropositive cases: ICD-10 codes: M050, M051, M051A-F, M052, M053, M058, M059.

†Seronegative cases: ICD-10 codes: M060, M068, M069.

‡Adjusted for age, calendar year of follow-up and educational level.

ICD-10, International Classification of Diseases, 10th version.