The aim of this pilot project is to determine the extent to which ALSPAC participants are exposed to arsenic. To carry out this aim, we propose to select 50 urine samples from ALSPAC participants to analyze for methylated arsenic species (inorganic arsenic, monomethylarsonic acid, dimethylarsinic acid). This will allow us to initially characerize the level of exposure to inorganic arsenic and determine whether it is scienitifcally worthwhile to pursue additional analyses on a larger pool of participants to test specific scientific hypotheses.