Atmospheric dispersion modeling for assessment of exposure to arsenic for epidemiological studies in the Nitra Valley, Slovakia

The short-range atmospheric dispersion model UK-ADMS has been applied to ca lculate ground-level concentrations of arsenic within 20 km of the Novaky P ower Plant, Nitra Valley, Slovakia, as a function of distance and direction from source and year of operation, for application to an assessment of loc al population exposure to arsenic, and hence to two epidemiological studies of the effect of arsenic exposure on skin, lung, and bladder cancer in an east European population. A simple approach, where the effect of complex te rrain is included by using local observations for meteorological input to t he model, is sufficient for initial screening to compare atmospheric disper sion with other exposure pathways. This shows that isopleths of ground-leve l annual average arsenic concentration in air (excluding periods when there is no wind) are elongated aligned with the axis of the valley. The maxima of concentration occur about 2 kin to the northeast and southwest of the so urce, and a factor of 30 reduction in concentration is found from there to a distance 10 km away. The value of this information for epidemiological st udies is discussed. If atmospheric concentration is found to be an importan t determinant of arsenic exposure for the Nitra Valley population, it will be necessary to carry out further investigation of the dispersion of the pl ume in complex terrain when there is no wind in the valley, which is the ca se in 13% of the observations and is estimated could contribute more than 5 0% of the annual average arsenic concentration close to the source.