Development of a sampling and analysis method for 4-vinyl-1-cyclohexene in air

The purpose of this research was to develop an applicable sampling and analytical method to determine airborne 4-vinyl-1-cyclohexene concentrations which are usually found in the atmosphere of polybutadiene factories. A solid sorbent tube, containing two sections (100 mg in the front and 50 mg in the back) of activated coconut-shell charcoal was chosen for sampling 4-vinyl-1-cyclohexene vapor. The 4-vinyl-1-cyclohexene in the charcoal samples was desorbed with carbon disulfide and analyzed by gas chromatography equipped with a flame ionization detector. The suitable air flow rate, adsorption capacity, sample storage stability, desorption efficiency and reliability of the method for sampling and analysis of 4-vinyl-1-cyclohexene were evaluated. The method was applied to sampling and analysis of 4-vinyl-1-cyclohexene in the rubber industry. The results indicated a suitable air flow rate of 0.3 to 1.5 l/min. The adsorption capacity of 4-vinyl-1-cyclohexene on 100 mg of charcoal was 0.2134 mg. The 4-vinyl-1-cyclohexene adsorbed on the charcoal was stable for 7 d at room temperature or 21 d in a refrigerated condition. The average percent desorption efficiency of 4-vinyl-1-cyclohexene ranged from 90.45% to 97.04% with the loaded amount ranging from 0.412 to 8.250 microg using 1 ml carbon disulfide. The limit of detection of 4-vinyl-1-cyclohexene was 0.044 ng. The average percent recoveries (n=6) of 4-vinyl-1-cyclohexene adsorbed on charcoal ranging from 0.46 to 8.87 microg were 96.78-102.87% with relative standard deviations (RSDs) of 0.34-1.92%, respectively. The concentrations of 4-vinyl-1-cyclohexene ranged from 0.011 to 0.105 mg/m(3) in the working environment of a polybutadiene factory.     

Repeated exposure to Opisthorchis viverrini and treatment with the antihelminthic Praziquantel lacks carcinogenic potential.

The effects of repeated Praziquantel administration, subsequent to infection and reinfection with Opisthorchis viverrini (OV), on lesion development in the Syrian hamster liver were investigated. Five applications of the antihelminthic drug were made (300 mg/kg body wt, i.g.), each time approximately 5 weeks after dosing with 60-80 OV metacercariae at weeks 0, 8, 16, 24 and 32. The animals were then maintained until week 40 when they were killed; histopathological investigation revealed no significant development of either hepatocellular of cholangiocellular preneoplastic/neoplastic lesions. The results indicate that repeated exposure to Praziquantel at levels sufficient for successful removal of parasite infestation does not itself carry carcinogenic risk.     

Histomorphological characteristics of cholangiocellular carcinomas in northeast Thailand, where a region infection with the liver fluke, Opisthorchis viverrini is endemic.

Northeast Thailand has a very high incidence rate of intrahepatic biliary tumors which is believed to closely related to infestation with the liver fluke, Opisthorchis viverrini. This study was conducted to ascertain whether there are any phenotypic differences in such tumors between northeast Thailand and Japan, a country free of liver flukes. Forty one intrahepatic cholangiocarcinomas from patients in northeast Thailand were histopathologically compared with 39 lesions collected in Japan. The proportions of each type of adenocarcinoma in the Thailand cases were similar to those of the Japanese cases except that medullary type poorly differentiated tubular adenocarcinoma was only found in the series from Thailand. Whether the presence of medullary lesions only in the cases from the area of endemic fluke infection implies differences in etiology remains in question. The similarity in the majority of histological types, the inflammatory reactions observed in the bile ducts and the earlier development of tumors in association with parasites suggests that tumor promotion resulting from liver fluke infection rather than quantitative or qualitative differences in genetic alterations is responsible for the high frequency of cholangiocellular carcinomas in northeast Thailand.     

An association between urinary cadmium and urinary stone disease in persons living in cadmium-contaminated villages in northwestern Thailand: a population study

Excessive urinary calcium excretion is the major risk of urinary stone formation. Very few population studies have been performed to determine the relationship between environmental cadmium exposure and urinary stone disease. This population-based study examined an association between urinary cadmium excretion, a good biomarker of long-term cadmium exposure, and prevalence of urinary stones in persons aged 15 years and older, who lived in the 12 cadmium-contaminated villages in the Mae Sot District, Tak Province, northwestern Thailand. A total of 6748 persons were interviewed and screened for urinary cadmium and urinary stone disease in 2009. To test a correlation between urinary excretion of cadmium and calcium, we measured urinary calcium content in 1492 persons, who lived in 3 villages randomly selected from the 12 contaminated villages. The rate of urinary stones significantly increased from 4.3% among persons in the lowest quartile of urinary cadmium to 11.3% in the highest quartile. An increase in stone prevalence with increasing urinary cadmium levels was similarly observed in both genders. Multiple logistic regression analysis revealed a positive association between urinary cadmium levels and stone prevalence, after adjusting for other co-variables. The urinary calcium excretion significantly increased with increasing urinary cadmium levels in both genders, after adjusting for other co-variables. Elevated calciuria induced by cadmium might increase the risk of urinary stone formation in this environmentally exposed population.