BTEX and Aldehyde Levels in Different Residential Environments: An Exploratory Case‐Control Study in Patients With Amyotrophic Lateral Sclerosis

This study is aimed at comparing the presence of BTEX (benzene, toluene, ethylbenzene, and o‐xylene and m,p‐xylene) and certain aldehydes (acetaldehyde and formaldehyde) in the residential environments of ALS patients (cases) and healthy individuals (controls). Moreover, a comparative analysis of indoor air pollutants in urban and rural areas to determine differences based on environment and housing type was performed, and the relationship between the presence of benzene and toluene in indoor air and the levels of their metabolites in the urine of the occupants was assessed. To this end, a cross‐sectional, case‐control, observational study was designed. Forty‐three locations (13 cases, 28 controls, and 2 positive controls) and two negative controls were analyzed. Passive samplers were used to measure BTEX (Tenax) and aldehydes (Radiello). t , t ‐Muconic acid and hippuric acid levels (metabolites of benzene and toluene, respectively) were quantified in urine using liquid chromatography. The indoor air comparative analysis between cases and controls showed no statistically significant differences. Higher formaldehyde levels were found in urban indoor environments compared to rural ones ( p < 0.001), based on the measurements from the 28 control subjects (analyzed separately as the case patients experienced changes in their daily routines due to their illness). Formaldehyde levels were also higher in apartment buildings than in detached houses ( p = 0.007). Finally, in the analysis of biological samples, no association was found between the levels of benzene and toluene in the air and the levels of t , t ‐muconic acid and hippuric acid in urine.