Archetypes of Spatial Concentration Variability of Organic Contaminants in the Atmosphere: Implications for Identifying Sources and Mapping the Gaseous Outdoor Inhalation Exposome

Whereas inhalation
exposure to organic contaminants can
negatively
impact human health, knowledge of their spatial variability in the
ambient atmosphere remains limited. We analyzed the extracts of passive
air samplers deployed at 119 unique sites in Southern Canada between
2019 and 2022 for 353 organic vapors. Hierarchical clustering of the
obtained data set revealed four archetypes of spatial concentration
variability in the outdoor atmosphere, which are indicative of common
sources and similar atmospheric dispersion behavior. “Point
Source” signatures are characterized by elevated concentration
in the vicinity of major release locations. A “Population”
signature applies to compounds whose air concentrations are highly
correlated with population density, and is associated with emissions
from consumer products. The “Water Source” signature
applies to substances with elevated levels in the vicinity of water
bodies from which they evaporate. Another group of compounds displays
a “Uniform” signature, indicative of a lack of major
sources within the study area. We illustrate how such a data set,
and the derived spatial patterns, can be applied to support the identification
of sources, the quantification of atmospheric emissions, the modeling
of air quality, and the investigation of potential inequities in inhalation
exposure.