[Study on occupational exposure limit of dimethoxymethane in workplace air].

OBJECTIVE: To study the occupational exposure limit of dimethoxymethane (DMM) in workplace air. METHODS: Literature research was conducted on DMM; information on its physicochemical properties, toxicology, and occupational epidemiology was collected. Upon analyzing these data, an occupational exposure limit of DMM in workplace air was proposed according to the guidelines and principles of developing occupational exposure limits for harmful factors in workplaces. RESULTS: A total of 165 air samples were collected from DMM manufacturers, 14 of which had a DMM concentration over 3000 mg/m(3), accounting for 8.48% of all samples. Compared with the control group, the exposed employees had a significantly increased incidence of discomfort symptoms when exposed to more than 6000 mg/m(3) DMN (P < 0.01).No significant differences in the constituent ratios of abnormal results in physical examinations were found between the exposure groups and control group (P > 0.05). CONCLUSION: We recommend to set the permissible concentration-time weighed average to 3100 mg/m(3) as the occupational exposure limit of DMM in workplace air in China. This occupational exposure limit standard meets the relevant requirements of toxicology and occupational epidemiology, as well as fits well with our country's current economical and technological levels. This standard has high applicability in China's domestic settings.

[A nitrite poisoning event associated with intentional chemical releases].

OBJECTIVE: To compare the field epidemiological investigation and the criminal investigation on a nitrite poisoning event caused by deliberate contamination. METHODS: Cases were searched according to the definition of the disease. Information on the histories of onset and diet of all the cases and normal population on site, were investigated face to face. Information as ingredients, processing and sales of foods was also gathered. Samples were collected and nitrite detection were performed. Relevant materials were searched, cases were interviewed and data related to criminal results were collected. RESULTS: Poisoned persons were staff of a big company in Longgang district of Shenzhen. The overall attack rate was 56.25% (63/112), with suspected and confirmed rates as 41.96% and 14.28%, respectively. The fatality rate was 3.17% (2/63). Clinical manifestation and effect of treatment were in accordance with the characteristics of an episode related to acute nitrite food poisoning in terms of factors as the time of onset, involving different age, sex and jobs of the patients. A total of 191 samples, including vomits from patients and seven batches of food and environment samples, were collected, with a positive detected rate of nitrite as 18.84%. Information gathered from the field environment, food distribution and processing supported the assumption that this was an incident of nitrite poisoning event with intention. RESULTS: from the criminal investigation showed that the suspect stemmed from the market management rivalry, bought nitrite, dissolved and spread on food stalls F9 and F10. CONCLUSION: This event of intentional nitrite release resulting in food contamination which further leading to food poisoning, was completely proved by the joint efforts of the teams and expertise from the field epidemiology survey and the criminal investigation.