Congratulations on a well researched article. At Trail, British Columbia, lead has accumulated in soils from the smelter operation for over 100 years. I helped to characterize the distribution of this and other metals in valley around the smelter and there is currently a program of soil remediation overseen by several experts and government agencies. I would only add to your article that lead in soils is difficult to characterize accurately, and can vary in concentration over a few meters distance depending on the form, method of dispersal, level of site disturbance, etc. Therefore if gardeners have their soil tested and the ppm concentration is > 300, I would recommend more sampling and trying to find out more about the soil and sources of contaminants. Covering a soil with a high lead concentration with landscape fabric does not help rule out continuous source input to soils, from groundwater or aerial deposition. This article is great, but when you high metals concentration over the CCME or CSR guidelines, you should ask more questions, in my opinion.