Hydrolyzes the toxic metabolites of a variety of organophosphorus insecticides. Capable of hydrolyzing a broad spectrum of organophosphate substrates and lactones, and a number of aromatic carboxylic acid esters. Mediates an enzymatic protection of low density lipoproteins against oxidative modification and the consequent series of events leading to atheroma formation. {ECO:0000269|PubMed:10479665, ECO:0000269|PubMed:15772423}. This is the function of PON1 (paraoxonase 1, Ensembl gene identifier ENSG00000005421).