(A) Contour maps showing of the smoothed, log transformed distribution of arsenic. *Marks the putative source of pollution at 44.5 33.0. (A) Contour maps showing of the smoothed, log transformed distribution of arsenic. *Marks the putative source of pollution at 44.5 33.0. (B) Contour maps showing of the smoothed, log transformed distribution of copper. *Marks the putative source of pollution at 44.5 33.0. F L R Williams, and S A Ogston Occup Environ Med 2002;59:2-8 ©2002 by BMJ Publishing Group Ltd