Comprehensive survey of radionuclides in contemporary smokeless tobacco products.

There is considerable interest in the chemical composition of smokeless tobacco products (STPs), owing to health concerns associated with their use. Previous studies have documented levels of 210Po, 210Pb and uranium in STP samples. Here, the levels of 13 α-particle and 15 ß-radiation emitting radionuclides have been measured in a broad and representative range of contemporary STPs commercially available in the United States and Sweden. For each radionuclide, the level of radioactivity and calculated mass per gram of STP are reported. The results indicate that, among 34 Swedish snus and 44 US STPs, a more complex radionuclide content exists than previously reported for these products. Of the 28 radionuclides examined, 13 were detected and quantified in one or more STPs. The most frequently identified radionuclides in these STPs were 40K, 14C, 210Po and 226Ra. Over half the STPs also contained 228Th, and an additional 8 radionuclides were identified in a small number of STPs. The presence of 14C, 3H and 230Th are reported in tobacco for the first time. The activity of ß-emitters was much greater than those of α-emitters, and the ß-emitter 40K was present in the STPs with both the greatest radioactivity and mass concentrations. Since the three radionuclides included in the FDA's HPHC list were either not detected (235U), identified in only three of 78 samples (238U), and/or had activity levels over fifty times lower than that of 40K (210Po, 238U), there may be a rationale for reconsidering the radionuclides currently included in the FDA HPHC list, particularly with respect to 40K. Using a model of the physical and biological compartments which must be considered to estimate the exposure of STP users to radionuclides, we conclude that exposure from α-emitters may be minimal to STP users, but 40K in particular may expose the oral cavities of STP users to ß-radiation. Although a more comprehensive picture of the radioisotope content of STPs has emerged from this study, epidemiological evidence suggests that the levels of radionuclides measured in this study appear unlikely to present significant risks to STP users.

Dosimetric equivalence of tar deposition in rodents and man.

It has proved very difficult to produce cancer in laboratory animals following the inhalation of tar from cigarette smoke. Amongst other factors, this may be due to the dose that animals get in comparison to humans. Data reported here suggest that the average dose to the bronchial region of the lung, estimated using radiotracer techniques, may be a factor of 4 lower. The local dose to the carinal is also discussed; this may be lower still.

Biological monitoring of occupational exposure in the chromate pigment production industry.

A survey of occupational exposure to hexavalent chromium in chromate pigment production was undertaken in factories producing lead chromate (PbCrO4) and strontium chromate (SrCrO4). Sampling pre and post-shift in a factory where SrCrO4 production had just started showed the optimum strategy for biological monitoring is the measurement of urinary chromium, in urine samples taken at the end of Friday shift and pre-shift the following Monday. However, short-term uptake may be assessed under these circumstances by the increase in urinary chromium over a shift. Body burden, representing long-term chromate exposure is best assessed by measuring chromium in whole blood or pre-shift urinary chromium at the beginning of the working week. Exceptionally high levels of chromium in blood (387-4160 nmol l-1) and urine (41-1250 nmol nmol-1 creatinine) as well as skin and nasal lesions, were discovered amongst the workforce at the strontium chromate plant. These contrasted with occupationally unexposed levels of less than 20 nmol l-1 and less than 1 nmol nmol-1 creatinine, respectively, and led to the continuation of the biological monitoring programme. At the same time, improved working practices and respiratory protection equipment were introduced. A steady elimination of chromium from whole blood with a half-life of approximately 24 days was found. This elimination rate was confirmed over a 14 day period when the workforce were completely removed from exposure. The study confirms the usefulness of biological monitoring in assessing the uptake of hexavalent chromium and control of exposure.