“…In other studies, calcium and strontium had been associated with house floors (Entwistle et al 2007;Konrad et al 1983;Middleton and Price 1996;Pierce et al 1998;Wells 2004;Wells et al 2007). In addition, potassium has been associated with wood ash and organic matter (Entwistle et al 2007;Knudson and Frink 2010;Knudson et al 2004b;Konrad et al 1983;Middleton and Price 1996;Misarti 2007;Pierce et al 1998;Wells 2004;Wells et al 2007). Finally, cluster 3, shown in white, exhibits the lowest overall mean concentrations of the following elements: iron, calcium, sodium, phosphorus, potassium, barium, strontium, titanium, lead, copper, and uranium (Fig.…”