Background A large body of cross-sectional studies have indicated a correlation between exposure to benzene series and increased rates of menstrual abnormalities in female workers, but these findings are confusing as evidence in the field of preventive medicine.

Objective To provide a more rigorous scientific basis for early prevention of reproductive function impairment through systematic review of independent studies.

Methods A comprehensive search was conducted for scientific articles published between January 1987 and July 2022, encompassing databases such as PubMed, Medline, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data, and CQVIP. A meta-analysis was conducted on literature that met the stringent criteria for case-control studies, featuring well-defined and consistent datasets. A meticulous investigation was executed to ascertain the collective odds ratio (OR) linked to menstrual abnormalities, encompassing diverse categories such as component, dosage, cumulative exposure dosage, and age groups. The prevalence and corresponding risk fractions were estimated by calculating frequency distributions and attributing risk percentages (AR).

Results A total of 53 papers of case-control studies were included in the meta-analysis, involving 27068 benzene series-exposed female workers and 22857 control female workers. During inhalation exposure to benzene series, benzene, toluene, and xylene all increased the risk of female menstrual abnormalities (OR=3.46, 95%CI: 2.79, 4.30, AR=29.37%). The OR value elevated with the increase of joint exposure concentration (OR=2.57-4.33), the OR value of the low cumulative exposure group was lower than that of the high cumulative exposure group (OR=2.81 vs 3.86, P < 0.01), and the OR value of the group aged 18 to 36 years old was higher than that of the group aged 18 to 45 years old (OR=5.83 vs 2.93, P < 0.01). The OR value discrepancy was apparent among the groups with single and multi-components of benzene, toluene, and xylene at different concentrations (OR=2.39-6.42, 95%CI: 1.26, 9.06). The symptom dimensions of menstrual abnormalities with a higher AR were abnormal menstrual volume (AR=47.12%), followed by abnormal menstrual cycle (AR=38.68%). The symptoms that were greatly influenced by the exposures were: irregular menstrual cycle (OR=3.33, 95%CI: 2.94, 3.79, AR=51.25%, n=1103), menorrhagia (OR=3.02, 95%CI: 2.76, 3.30, AR=46.73%, n=2262), dysmenorrhea (OR=3.22, 95%CI: 2.69, 3.84, AR=44.18%, n=3183), and prolonged menstrual duration (OR=2.20, 95%CI: 1.99, 2.43, AR=37.02%, n=1452).

Conclusion  Through inhalation exposure to benzene series, a higher concentration of combined benzene, toluene, and xylenes may increase the risk of menstrual abnormalities in female workers of childbearing age. The OR value of menstrual abnormalities is varied by chemical composition, exposure dose, cumulative exposure dose, and age. Volume and cycle of menstruation are affected by the exposure, and the most common symptoms are dysmenorrhea, menorrhagia, irregular cycle.