Simulations in health risk assessment.

Health risk assessment procedure provides a clear and systematic form of quantitative (or semi-quantitative) description of environmental health impact. It is well known that this approach is burdened with various types of uncertainties of different origin and nature. Therefore, the results of risk assessment should always contain both the "number" and the "measure of uncertainty". The problem is that even if one does attempt to take account of the uncertainty, one does not know a priori what is the probability of getting a given risk value within the specified range of uncertainty. A promising tool for the assessment of risk which provides a means of describing the sensitivity with respect to different exposure factors and evaluating different intervention scenarios is the technique of Monte Carlo simulation. In this probabilistic approach all variables and parameters used in risk assessment may be regarded as distributions throughout the analysis. A process of repeated simulations is then used, during which the estimated quantity (risk in this case) is calculated many times (usually 10,000 or more) with randomly chosen values of variables and parameters, covering their range of variability and reproducing the assumed distribution density. The final result is given in the form of a probability distribution of risk. The idea of Monte Carlo simulations in health risk assessment concerning the exposure to heavy metals in drinking water is illustrated in the population living in the vicinity of the "Lubna" waste site, taken as an example.

Air pollution and acute respiratory diseases in children: regression analysis of morbidity data.

The aim of this study was to investigate the relationship between acute respiratory diseases and the air quality in the urban area of the Upper Silesian Industrial Zone during autumn and winter with special emphasis on temporal variability in the air concentrations of pollutants. The survey was carried out in 5 primary care units in Chorzów where the morbidity data on the selected respiratory diseases were collected from 1 November 1992 to 31 March 1993. The air pollution data were obtained from the monitoring station, being a part of the Sanitary and Epidemiological Station Network. Regression analysis with mean values of concentrations of air pollutants as explanatory variables revealed a positive effect of combined suspended particulate matter and SO2 concentration on the increased prevalence of bronchitis and bronchiolitis. Similar and even stronger effect was observed at the level of temporal variability coefficients of the air pollutants. A hypothesis that temporal variability of the air concentration of pollutants might be a more relevant factor for determining the prevalence of respiratory diseases than simple mean values of the pollutant concentrations is very interesting worthy of further investigations.

Results of the health survey of a population living in a vicinity of a large waste site (Warsaw, Poland).

Although attracting rapidly increasing attention from the public, the health impact of environmental exposures related to the operation of waste dumping sites is a relatively new issue in Poland. However, the problem cannot be neglected in light of the fact that environmental impact assessment in selected sites revealed the lack of sufficient documentation concerning quantity and quality of dumped materials and poor technological management of the sites. The paper describes the results of health survey performed in a vicinity of a country's largest municipal waste site. Although the study came across methodological obstacles involving low participation and difficult to estimate representativeness of the examined group its findings obtained in 393 adults and 188 children and the results of internal comparisons revealed some interesting observations. Three "exposure-classification" variables were used in data analysis (geographical location, distance, "waste traffic" intensity) and health status was examined by means of self- and physician-administered questionnaire, physical examination and routine laboratory analyses. Relationship, although weak, of subjective symptoms and objective findings with the place of residence vis-a-vis the waste site location suggests that potential health effects of waste site-related environmental exposures might include psychological problems, digestive tract disorders and respiratory disorders as well as allergic symptoms. An intriguing observation concerning pregnancy-related health outcomes was made. The exact role of environmental determinants in this respect remains unclear and should be addressed by specific environmental epidemiological and toxicological studies. The findings as well as subjects' concern about health consequences of exposures to waste-related pollution (paralleled by subjective perception of impaired health) justify further investigations and public health initiatives including environmental impact assessment and health monitoring activities targeting populations living in a vicinity of waste sites in Poland.

Fundamental chemistry of iodine. The reaction of di-iodine towards thiourea and its methyl-derivative: formation of aminothiazoles and aminothiadiazoles through dicationic disulfides.

The reactivity of di-iodine towards thiourea (TU) and its derivative methylthiourea (MeTU) was studied. A diversity of products was obtained from these reactions. TU reacted with di-iodine in the absence or presence of hydroiodic or hydrochloric acids in a 1 : 1, 1 : 1 : 1 or 1 : 1 : 2 (TU : I2 : HX (X = I, Cl)) molar ratio to form the ionic compounds [(TU2)(2+)2(I(-))·H2O] (1), [2(TU2) (2+)·(Cl(-))·2(I(-))·(I3(-))] (2) and [(TUH)(+) (I3(-))] (3). The compounds [(TU2)(2+)(Br(-))(I3(-))] (4) and [(TU2)(2+)2(Br(-))·H2O] (5) were derived from the reactions of TU with di-iodine in the presence of hydrobromic acid in a 1 : 1 : 1 or 1 : 2 : 1 (TU : I2 : HBr) molar ratio. However, when the product of the reaction between TU and di-iodine in a 2 : 1 (TU : I2) molar ratio was crystallized in acetone-ethylether media the ionic salt of formula [(DAThdH(+))(I(-))] (6) (DAThd = 3,5-diamino-1,2,4-thiadiazole) was obtained. Methylthiourea (MeTU) reacted with di-iodine in the presence of hydrobromic acid (1 : 1 : 1, MeTU : I2 : HBr) in dichloromethane to form a solid product which gives [2(MeTU2) (2+)·(2Br(-))(I4(2-))] (7). Moreover, MeTU reacted with I2 in 2 : 1 (MeTU : I2) to form an intermediate powder product which was crystallized in acetone to give the 2-amino-3,4-dimethylthiazolium cation in [(DMeAThH(+))(I(-))(H2O)] (8). Upon changing the crystallization medium to ethanol, instead of acetone, the cationic 5-amino-3-methylamino-4-methyl-1,2,4-thiadiazolium (AMeAThdH)(+) in [(AMeAThdH(+))(I3(-))] (9) was formed. The compounds were characterized by m.p., FT-IR, UV-Vis, (1)H-NMR spectroscopy and mass spectrometry. The crystal structures of compounds 1-9 were determined by X-ray crystallography.

Blood lead levels in children: epidemiology vs. simulations.

The key problem in environmental health is to identify the potential health hazards at the lowest possible cost based upon available environmental data. Biokinetic models such as IEUBK Lead 0.99d are very promising in this respect. We attempted a comparison between epidemiological data and predictions of the model. As input, we used the existing exposure data for the Katowice Voivodship (administrative district, Poland). Epidemiological analysis was based on the results of the screening programme 'Prevention of the Environmental Lead Intoxication in Children Living in Katowice Voivodship'. The simulations consisted of predicted distributions of blood lead levels in children. They have been compared with observed distributions. Sensitivity analysis of simulations with respect to lead concentration in air, soil, water and diet has also been performed. The agreement between predicted and observed mean blood lead levels was quite good (relative difference of about 40%) as for the coarse exposure assessment employed. At the level of risk (fraction of population having blood lead levels exceeding 10 microg/dl) the difference is much higher (about a factor of 2). In order to explain this discrepancy we checked the goodness of fit for the log-normal distribution function (usually taken as a template distribution for lead in the population) in the right tail of the distribution. We noticed a systematic effect depleting the right tail of the actual distribution as compared with the log-normal one. Therefore one can expect that using (as a template) another skewed distribution better fitted in the right tail would improve the accuracy of risk assessment.