Lead Poisoning and Intelligence: A Search for Cause and Effect in the Scottish Mental Surveys

Figure 1

Map of median topsoil pH in Scotland^∗. The location of each administrative region participating in the 1947 Survey is also shown. The map is constructed from data representing more than 40,000 analyses held within the Scottish soils database. Each open circle shows the approximate geographic center of the respective educational administrative region. Each region, which consisted of 2 or more pre-1974 Scottish counties, is numbered. Along with the number is given the mean Survey test score for the region. The two “star” symbols indicate the locations of the primary source of drinking water for Edinburgh (Talla Reservoir) and Glasgow (Loch Katrine) at the time of the Surveys (see text). Glasgow is part of group 8 while Edinburgh belongs to group 5 (^∗contains James Hutton Institute material (copyright 2018) (http://ukso.org/SoilsOfScotland/home.html)).