Exposure to polycyclic aromatic hydrocarbons in occupational versus urban environmental air.

OBJECTIVES: To evaluate the balance between occupational and environmental exposure to suspended particulate matter (SPM) and polycyclic aromatic hydrocarbons (PAHs), comparison measurements were performed in a coal-fired power plant and the urban atmosphere from the town nearby. METHODS: The analysis of SPM for PAH content was done according to a high-performance liquid chromatography (HPLC)-based method. The microscopic assessment was performed using scanning electron microscopy (SEM) by silver coverage of the samples derived by air filter. RESULTS: Contrary to expectations, the results showed low levels of particle-bound PAHs in the occupational environment (< 1 ng benzo(a)pyrene/m3 air) and high levels in urban air (range 80-1250 ng benzo(a)pyrene/m3). The SPM collected from the power plant exhibited non-respirable characteristics (particles larger than 10 microm), whereas urban SPM almost exclusively contained respirable airborne particles (<3 microm). CONCLUSIONS: The PAH burden, combined with the enhanced probability of respiratory absorption, confers a much greater hazard potential to the urban SPM. Under these conditions, in areas or countries in which old technologies remain in use, occupational exposure to SPM containing PAHs might represent a severe underestimation of the total risk as it does not take into account the background air pollution.

Swimming pool chlorination: a health hazard?

A pilot study addressed potential effects of long-term exposure to chlorination products in swimming pools. The indicator compound chloroform was detectable in blood from competitive swimmers in an indoor pool (mean = 0.89 +/- 0.34 microgram/l; n = 10), but not in outdoor pool swimmers. No hepatotoxic effect was indicated by serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) or gamma-glutamyl transpeptidase (gamma-GT) enzyme levels. beta-2-microglobulin, an indicator of renal damage, was significantly elevated in urine samples of the slightly, but significantly, younger indoor swimmers. The precise ratio between these 2 possible causes, age and chloroform exposure, as well as the mechanism of the former, remain to be elucidated.

Active biomonitoring of polycyclic aromatic hydrocarbons by means of mosses.

Spherical bags, packed with 20 g of peat moss (Sphagnum spp.), were exposed to ambient air at a distance of 1 km from a plant manufacturing electrodes for the production of aluminium, near Rotterdam, The Netherlands. In these bags, the concentrations of six polycyclic aromatic hydrocarbons were determined, and compared with the concentrations in moss bags that had been exposed in relatively clean areas. From the results it can be concluded that, in addition to their useful application for biomonitoring of heavy metals, mosses can be applied in active biomonitoring of polycyclic aromatic hydrocarbons in ambient air.

Detoxification of mercury, cadmium, and lead in Klebsiella aerogenes NCTC 418 growing in continuous culture.

Klebsiella aerogenes NCTC 418 growing in the presence of cadmium under glucose-, sulfate-, or phosphate-limited conditions in continuous culture exhibited sulfide formation and Pi accumulation as the only demonstrable detoxification mechanisms. In the presence of mercury under similar conditions only HgS formation could be confirmed, by an increased sensitivity to mercury under sulfate-limited conditions, among others. The fact that the cells were most sensitive to cadmium under conditions of phosphate limitation and most sensitive to mercury under conditions of sulfate limitation led to the hypothesis that these inorganic detoxification mechanisms generally depended on a kind of "facilitated precipitation". The process was coined thus because heavy metals were probably accumulated and precipitated near the cell perimeter due to the relatively high local concentrations of sulfide and phosphate there. Depending on the growth-limiting nutrient, mercury proved to be 25-fold (phosphate limitation), 75-fold (glycerol limitation), or 150-fold (sulfate limitation) more toxic than cadmium to this organism. In the presence of lead, PbS formation was suggested. Since no other detoxification mechanisms were detected, for example, rendering heavy metal ions innocuous as metallo-organic compounds, it was concluded that formation of heavy metal precipitates is crucially important to this organism. In addition, it was observed that several components of a defined mineral medium were able to reduce mercuric ions to elemental mercury. This abiotic mercury volatilization was studied in detail, and its general and environmental implications are discussed.

Inorganic phosphate accumulation and cadmium detoxification in Klebsiella aerogenes NCTC 418 growing in continuous culture.

Klebsiella aerogenes NCTC 418, growing in the presence of cadmium under glucose-, sulfate-, or phosphate-limited conditions in continuous culture, exhibits two different cadmium detoxifying mechanisms. In addition to sulfide formation, increased accumulation of Pi is demonstrated as a novel mechanism. Intracellular cadmium is always quantitatively counterbalanced by a concerted increase in both inorganic sulfide and Pi contents of the cells. This led to the conclusion that production of sulfide and accumulation of Pi are detoxification mechanisms present in K. aerogenes but that their relative importance is crucially dependent on the strain and the growth conditions employed.

Adaptation to Cadmium by Klebsiella aerogenes Growing in Continuous Culture Proceeds Mainly via Formation of Cadmium Sulfide.

The adaptation of Klebsiella aerogenes to high levels of cadmium was studied in continuous culture under conditions of glucose limitation. When up to 6 x 10 M cadmium was added to a culture in steady state, growth ceased instantaneously but resumed within 5 h (dilution rate, 0.1 h). When again in steady state, these adapted cells exhibited a far greater tolerance to cadmium than did unadapted cells (not previously exposed to cadmium) when tested on solid media containing different concentrations of cadmium. This relative insensitivity of adapted cells to cadmium was subsequently lost in continuous culture within 5 days after omitting cadmium from the influent medium. Thus, the phenomenon was an inducible physiological process. Adapted cells contained substantial amounts of cadmium (up to 2.4% of the bacterial dry weight). The cadmium content of the cells was dependent on growth conditions and was found to be proportional to the inorganic sulfide content of the cells in all cases. This suggested that formation of CdS is probably the most important mechanism of detoxification in this organism. The presence of large numbers of electron-dense granules on the cell surface (absent in cultures without added cadmium) provided additional support for this conclusion.

Response of Rhodopseudomonas capsulata to illumination and growth rate in a light-limited continuous culture.

Rhodopseudomonas capsulata was grown under anaerobic, photosynthetic conditions in a continuous culture device. Under light limitation, at a constant dilution rate, it was shown that cell composition, including photopigment (bacteriochlorophyll and carotenoids) and ribonucleic acid content, was not affected by incident light intensity; however, steady state culture density varied directly and linearly with light intensity. On the other hand, photopigment and ribonucleic acid levels were affected by growth rate regardless of light intensity. Additional experiments indicated a high apparent Ks for growth of R. capsulata with respect to light. These results were interpreted to mean that near the maximum growth rate (D = 0.45 h-1) some internal metabolic process became the limiting factor for growth, rather than the imposed energy limitation. A mathematical expression for the relation between steady-state culture density and dilution rate was derived and was found to adequately describe the data. A strong correlation was found between continuous cultures limited either by light or by a chemical energy source.

Influence of specific growth limitation and dilution rate on the phosphorylation efficiency and cytochrome content of mitochondria of Candida utilis NCYC 321.

With Candida utilis cells that had been removed directly from a 61 chemostat culture, in steady state, well-coupled mitochondria generally could be isolated. This requires a modified snail-gut enzyme procedure that allowed the total processing time to be decreased to 3 h, or less. Examination of these mitochondria in an oxygraph showed the presence of 3 sites of energy conservation when the cells were grown at various dilution rates between 0.1 and 0.45 h-1 in environments that were, successively, glucose-, ammonia-, magnesium-, phosphate- and sulphate-limited. Potassium-limited cells also apparently possessed 3 sites of oxidative phosphorylation when growing at dilution rates greater than 0.2 h-1, but only 2 sites when growing at lower dilution rates. Analysis of cytochrome spectra obtained with these intact mitochondria revealed large quantitative (but not qualitative) differences, depending on the environmental conditions under which the yeast had been cultured. In particular, comparison of the ratio of cytochrome b to cytochrome a showed a pattern of change with dilution rate in mitochondria from potassium-limited cells that was distinctly different from those evident in mitochondria from cells that had been limited in their growth by the availability of other nutrients.

Growth and physiology of Candida utilis NCYC 321 in potassium-limited chemostat culture.

When grown in a defined simple salts medium, plus vitamins, Candida utilis displayed an absolute requirement for potassium. But the potassium content of this yeast was exceedingly variable and, with aerobic chemostat cultures (grown at a dilution rate of 0.1 h-1; 30 degrees C; pH 5.5), was low (less than 0.2%, w/w) when they were potassium-limited and high (greater than 2%, w/w) when glucose-limited. With potassium-limited cultures, the cell-bound potassium content also varied markedly with growth rate, though hardly at all with glucose-limited cultures; magnesium- and phosphate-limited cultures gave intermediate responses. Changes in cell-bound potassium content correlated only weakly with changes in the cellular contents of magnesium, phosphate and RNA, but strongly with changes in both the Yglucose and Y0 values, indicating an involvement of potassium in the generation of energy by oxidative phosphorylation reactions and/or the utilization of this energy for growth processes. Studies with isolated mitochondria revealed that potassium-limited organisms had a changed content of cytochrome b relative to cytochrome a, and lacked coupling at either site 2 or site 3 of the respiratory chain. These results are discussed in relation to the reported functions of potassium in the growth of micro-organisms, and the organizational differences between prokaryotic and eukaryotic cells.