Objective: To determine the cause of acute poisoning occurred in a factory in Yangjiang city, Guangdong province.
Methods: In a cross-sectional study, interviews were conducted with the administrators of the factory and the local physician. A review was conducted on the water system used for industrial purposes and a separate system used by workers for drinking water. Treatment and discharge of industrial waste water were examined. Face-to-face interview was conducted to identify risk of exposure for illness among workers.
Results: A total number of 36 cases were identified in the plant and the attack rate was 16.4% (36/220). The incubation period (time between drinking polluted water and the onset of symptoms) had a median of 90 minutes (range: 30 - 230 minutes). Consuming water at the factory increased the attack rate and a dose-response effect was identified (chi(2)(trend) = 79.115, P < 0.01). The nitrite content of residuals in drinking water exceeded the WHO standard (1 ppm).
Conclusions: The accident of acute poisoning was due to drinking water contaminated with sodium nitrite. The prevention of drinking water contaminated by toxic chemicals like sodium nitrite, and the design of industrial and potable water supply system need to be carefully reviewed. Regulations should be developed and enforced to minimize the impact of industrial waste water discharges to guarantee the access to clean drinking water.