Objective  To analyze two maleic anhydride poisoning accidents involving multiple workers which were caused by cargo handling of maleic anhydride, so as to attract the attentions of both employees and employers and avoid future recurrence of similar poisonings.

Methods The enterprise managers and workers were interviewed to collect information on 24 workers' in cident of disease and medical process. The patients' medical records were retrieved. Meanwhile, a workplace spot investigation was also conducted.

Results The poisoning accidents were caused by chemical dust leakage from broken packing bags. According to the national Diagnostic Criteria of Occupational Acute Toxic Respiratory System Disease, the poisoning cases were diagnosed as occupational acute maleic anhydride exposure reaction (n=13) and mild (n=8) or moderate (n=3) poisoning.

Conclusion The two accidents of occupational acute maleic anhydride poisoning resulted from chemical dust leakage from broken packing bags suggest the underlying causes are the lack of hazardous chemicals management, health education, and protective measures in enterprises and also weak protective awareness in workers.