To determine the demographic and environmental exposure characteristics of participants in the National ALS Biorepository (Biorepository) and compare the blood levels of cadmium (Cd), lead (Pb), selenium (Se), manganese (Mn), and total mercury (tHg) to National Health and Nutrition Examination Survey (NHANES) participants.

Amyotrophic lateral sclerosis (ALS) is a rare and fatal disease of the upper and lower motor neurons. While 10% of ALS cases is hereditary, a gene-environment interaction is believed to be the main contributor in many sporadic cases. Elevated heavy metals in blood have been implicated in the pathology of several neurodegenerative diseases. We hypothesize the ALS cohort to have greater levels of blood heavy metals than NHANES participants.

Blood samples from Biorepository participants (n=549) collected in 2013–2015 and 2017 were analyzed following the same protocol used to analyze the subset of NHANES cohort (n=10,809) during 2013-2018. We report descriptive summary in demographic (age/sex/race/education/military history) and comparison of blood metal level means using t-test. Further, self-reported occupational- and non-occupational environmental exposures to pesticides, chemicals, and metals were described for Biorepository participants with available environmental risk factor data. NHANES analyses used survey weights and accounted for the complex design to generate nationally representative estimates. 

ALS Biorepository participants had higher geometric means of blood level Cd, Pb, Se, and tHg compared to NHANES cohort. Among the Biorepository participants, exposure to pesticides (90.3%), chemicals (80.7%) and metals (85.8%) from non-occupational settings were self-reported in higher frequency than occupational exposure to these substances.

Blood metal levels were elevated in ALS Biorepository participants compared to NHANES. Self-reported non-occupational exposures to pesticides, chemicals, and metals were more common than occupational exposures. Determining a potential association between blood metals and exposure history in our cohort can help further understand the role of environmental exposure in the etiology of ALS.