sodium-nitrite and Carcinoma

The objective of this study is to investigate the risk of esophageal carcinoma in a cohort with long-term occupational exposure to sodium nitrite. The method used was a retrospective cohort study. A small wood screw manufacturer was founded in 1977 and closed down in 2000. In their production process, the sodium nitrite solution was used to serve as anticorrosive and coolant fluid. One hundred sixty workers in turning and milling shops had direct exposure to sodium nitrite through skin, mouth, and airway because of lack of occupational protective knowledge (study group), whereas 255 workers from other workshops without direct contact with sodium nitrite served as control group. The incidence, diagnosis, and treatment of esophageal carcinoma as well as other malignant tumors in these two groups were followed until the end of 2007. The sodium nitrite exposure time in the study group ranged from 16 to 23 years, with an average of 22.1 years. During 30 years of follow-up, there were 11 esophageal carcinomas and 10 other malignant tumors (4 hepatic cell carcinomas, 3 lung cancers, 2 breast cancers, and 1 leukemia) documented in the study group, while no cancer developed in the control group. The risk for esophageal carcinoma was significantly increased in the study group compared with the control group (relative risk = 1.26, 95% confidence interval = 1.08-1.46, chi-square = 116.83, P < 0.001). Long-term exposure to sodium nitrite markedly increases the risk of esophageal carcinoma in human body.

Topics: Adolescent; Adult; Aged; Breast Neoplasms; Carcinoma; Chi-Square Distribution; China; Construction Materials; Esophageal Neoplasms; Female; Follow-Up Studies; Humans; Incidence; Kaplan-Meier Estimate; Leukemia; Liver Neoplasms; Lung Neoplasms; Male; Middle Aged; Occupational Exposure; Retrospective Studies; Risk; Sodium Nitrite; Young Adult

Cancers and precancerous lesions of the esophagus were efficiently induced in rats by the simulation of a clinico-epidemiological setting; that is, the administration of precursors of nitrosamine. Six week old non-inbred male Wistar rats were given 2g/kg bodyweight of sarcosine ethyl ester hydrochloride (SEEH) and concurrently 0.3g/kg bodyweight of sodium nitrite (NaNO2), precursors of N-nitrososarcosine ethyl ester (NSEE), in 2% sucrose as drinking water. Group 1 received the precursors twice a week for 6 weeks followed by 8 weeks observation, and group 2, once every 3 days for 7 weeks followed by 26 weeks observation. At the end of treatment, no tumor had developed in the esophagus of rats in group 1, but the [3H]-thymidine labeling indices in both basal and superficial layer cells were higher than in the control group. On subsequent observation, papillomas appeared in group 1 (33.3%), and carcinomas in group 2 (33.3%), within 4 weeks. The tumors induced in group 1 were mostly papillomas and rarely carcinomas. When the observation was prolonged in group 2, 100% of the animals had cancer in week 20. The pathological changes of the lesions paralleled the sequential development of human squamous cell carcinoma of the esophagus. Our system has the advantages in that papillomas and cancers can be induced in rats in a short time and the agents used are less toxic than preformed nitrosamines administered previously by gastric intubation. It would serve as a useful experimental tool to study premalignant lesions and cancers of the esophagus.

Topics: Animals; Carcinogens; Carcinoma; Disease Models, Animal; Esophageal Neoplasms; Male; Nitrosamines; Precancerous Conditions; Rats; Rats, Wistar; Sodium Nitrite

Sodium nitrate was given to male noninbred Wistar rats at levels of 800 ppm and 1,600 ppm in a pellet diet for 646 experimental days. The first tum or was found on day 441 in the liver of a rat given a diet containing 800 ppm sodium nitrite. On day 646, liver tumors were found in 1 of 22 rats (4.5%) on an 800-ppm sodium nitrite diet and in 5 of 19 rats (26.3%) on a 1,600-ppm sodium nitrite diet. The incidence of liver tumors in the rats fed 1,600 ppm sodium nitrite was significantly different from that in controls as judged by the t-test (P < 0.05). A hepatocellular carcinoma and a hemangioendothelial sarcoma of the liver were found on day 646 in 2 rats fed 1,600 ppm sodium nitrite. One mammary tumor but no liver tumors were found in the 19 control rats. The concentration of sodium nitrite decreased after preparation of the pellet diet, but it was still at least 70% of the initial amount when the pellets were given to the rats. Volatile N-nitroso compounds, especially dimehylnitrosamine, at ppm levels were detected in the pellet diet with a gas chromatography-thermal energy analyzer.

Topics: Adenoma; Animals; Carcinogens; Carcinoma; Diet; Dose-Response Relationship, Drug; Hemangiosarcoma; Liver Neoplasms; Male; Neoplasms, Experimental; Nitrites; Nitroso Compounds; Rats; Sodium Nitrite; Time Factors