The tobacco plant contains nickel and several other toxic metals, most probably absorbed from the soil, fertilizing products or from pesticides. It has been stated that nickel in a burning cigarette might form the volatile, gaseous compound, nickel tetracarbonyl, and thereby be introduced into the respiratory tract. Accordingly, the main objective of the present study was to find out if nickel content in inhaled smoke from ordinary cigarettes and nickel-contaminated cigarettes handmade by nickel process workers might be a supplementary source of nickel exposure to cigarette smoking process workers leading to additional risk of occupational respiratory cancer in these workers. Blood and urine samples from 318 randomly selected employees from Falconbridge Nickel Refinery in Kristiansand, Norway, allocated to 197 smokers and 121 non-smokers, were analysed for nickel content. Nickel quantities in tobacco from various cigarette brands, from nickel-contaminated cigarettes made by process workers or from cigarettes added known amounts of various nickel salts were analysed before being smoked. The cigarettes were smoked in a smoking machine device applying an electrostatic filter. Blood and urine, tobacco, ash and precipitates in the filter from the main stream smoke of the cigarettes were analysed for nickel quantities by atomic absorption spectrometry methods as previously described by the authors. The nickel concentrations in blood plasma and urine were quite similar among smokers and non-smokers, 6.2 and 48.1 microg L(-1) in smokers, and 6.4 and 50.5 microg L(-1) in non-smokers respectively. We recovered 1.1% or even less of nickel in the mainstream smoke after smoking the entire cigarettes without leaving any butt. Most of the tobacco nickel was recovered in the ash. We conclude that the inhaled nickel in the working atmosphere is probably the main source of the nickel exposure to the respiratory tract in these workers. It remains to be determined why cigarette smoking still seems to be a decisive cofactor in the development of respiratory tract cancer in nickel workers.

Earlier work-related lung and nasal cancer studies included estimates of exposures to different nickel species in the refinery. Based on the metallurgy, only insoluble nickel was believed to be present around the roasters but mixed exposure was assumed in most areas, including the tankhouse. Occasional leaching tests of samples from the roaster area have indicated the presence of soluble nickel. This study reports on five parallel sets of dust samples collected from different floors with standard equipment and treated as follows. Two sets were leached with an ammonium citrate buffer at pH 4.4. Undissolved material was treated with HClO 4 /HNO 3 , evaporated to dryness and dissolved in HCl. Ni, Cu, Co, Fe, Se, and As were determined in both fractions. Water soluble Ni was found in all samples, ranging from 5-35%. Sulfate in the solutions correlated nearly stoichiometrically to the total metal content. The three remaining sets were investigated by, respectively, differential leaching, X-ray diffraction and scanning electron microscopy. The percentage of soluble nickel found by differential leaching corresponded well with those obtained by the simplified procedure. X-Ray diffraction analysis showed the presence of NiSO 4 •6H 2 O as well as oxides of Ni and Cu. This study indicates mixed exposures also in the roaster area. It also clearly indicates that basing exposure on the metallurgy alone can lead to serious misjudgements. The impact of this new information on the interpretation of cancer incidence at this refinery must await the analysis in an ongoing case-reference study.

We describe and evaluate a method for determining nickel in plasma and urine by atomic absorption spectrometry. Proteins are precipitated with trichloroacetic acid and sulfuric acid; ammonium pyrrolidinedithlocarbamate is used as the chelating agent for nickel, and methyl isobutyl ketone as extraction solvent. The results were compared with results obtained by the acid-digestion technique for removing proteins and other organic substances. Analyses for both plasma and urine were better by the present procedure. The mean and standard deviation for nickel in plasma from 15 healthy individuals was 2.13 +/- 0.58 microgram/liter by this method. For nickel in urine from 15 healthy men the mean and standard deviation was 4.45 +/- 1.9 microgram/liter. The coefficient of variation for plasma was 11.9%, and for urine 12.2% in 10 analyses of the same plasma and urine with the protein-precipitation procedure, as compared with 26.0 and 38.2%, respectively, by the acid-digestion technique.

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Dry weight and Relative Growth Rate of Lemna gibba were significantly increased by CO2 enrichment up to 6000 μl CO2 l(-1). This high CO2 optimum for growth is probably due to the presence of nonfunctional stomata. The response to high CO2 was less or absent following four days growth in 2% O2. The Leaf Area Ratio decreased in response to CO2 enrichment as a result of an increase in dry weight per frond. Photosynthetic rate was increased by CO2 enrichment up to 1500 μl CO2 l(-1) during measurement, showing only small increases with further CO2 enrichment up to 5000 μl CO2 l(-1) at a photon flux density of 210 μmol m(-2) s(-1) and small decreases at 2000 μmol m(-1) s(-1). The actual rate of photosynthesis of those plants cultivated at high CO2 levels, however, was less than the air grown plants. The response of photosynthesis to O2 indicated that the enhancement of growth and photosynthesis by CO2 enrichment was a result of decreased photorespiration. Plants cultivated in low O2 produced abnormal morphological features and after a short time showed a reduction in growth.