Distributions of lead and cadmium in dust in the vicinity of a sewage sludge incinerator

The content of lead and cadmium in surface dust within a 4 km radius of a sewage sludge incinerator has been investigated. Particular attention was given to Pb and Cd in different size fractions of dust, an aspect not explored in previous studies, and the differences between expressions of contamination as concentration or loading were examined. Despite suggestions from reports that sludge incinerators may have difficulty in complying with emission standards, the present investigation found little evidence for a major contribution to local pollution by the incinerator. Certainly, the highest Cd level was found some 2.2 km downwind of the prevailing wind direction from the incinerator, suggesting some resultant contamination, although the levels do not appear to be excessive. Similar observations apply to Pb contamination of the area. While data of the type produced in this study contribute to an understanding of environmental quality, both loadings and levels need to be considered, as the implications of only consideration one of these may be limited and even misleading.