Airborne contaminants associated with ALS risk. Volcano plot depicts airborne contaminants from the 2008 NEI database that met the FDR cutoff <0.2 for association with ALS risk in the ‘discovery cohort’. The y-axis shows the negative logarithm of the p-value, such that the lowest p-values are at the top. The x-axis shows the logarithm of the fold change (Log(FC)), with contaminants associated with decreased ALS risk on the left, and those that increase risk on the right. Contaminants that are most statistically significant (red) and have the largest fold change representing increased ALS risk fall in the top, right-hand side of the figure, including Lead and the PCBs (Hep = Heptachlorobiphenyl; X2_PCB = 2_Chlorobiphenyl_PCB_1; Hex = Hexachlorobiphenyl; Pen = Pentachlorobiphenyl; X244 = 2,4,4_Trichlorobiphenyl_PCB_28).