Enhanced Nontarget Screening Algorithm Reveals Highly Abundant Chlorinated Azo Dye Compounds in House Dust

Humans
spend 90% of their time indoors, but the majority of indoor
pollutants remain unknown. In this study, a nontarget screening algorithm
with reduced false discovery rates was developed to screen indoor
pollutants using the Toxic Substances Control Act (TSCA) database.
First, a putative lock mass algorithm was developed for post-acquisition
calibration of Orbitrap mass spectra to sub-ppm mass accuracy. Then,
a one-stop screening algorithm was developed by combining MS1 spectra, isotopic peaks, retention time prediction, and in silico MS2 spectra. A sufficient true positive
rate (73%) and false discovery rate (5%) were achieved for the screening
of halogenated compounds at a score cutoff of 0.28. Above this cutoff,
427 chemicals were detected from 24 house dust samples, including
39 chlorinated compounds. While some identified halogenated compounds
(e.g., triclosan) are well known, 18 previously unrecognized
chlorinated azo dyes were detected with high abundance as the largest
class of chlorinated compounds. Two chlorinated azo dyes were confirmed
with authentic standards, but the two most abundant chlorinated azo
dyes were missed by the algorithm due to the limited breadth of the
TSCA database. These compounds were annotated as chlorinated analogues
of Disperse Blue 373 and Disperse Violet 93 using the DIPIC-Frag method.
This study revealed the presence of highly abundant chlorinated azo
dyes in house dusts, highlighting their potential health risks in
the indoor environment.