  Evaluating human exposure to environmental hazards is crucial for identifying
susceptible communities and devising targeted health policies. Standard
environmental hazard exposure assessment methods have been primarily based on
place of residence, an approach which neglect individuals hazard exposures due
to the daily life activities and mobility outside home neighborhood. To address
this limitation, this study proposes a novel mobility-based index for hazard
exposure evaluation. Using large-scale and fine-grained human mobility data, we
quantify the extent of population dwell time in high-environmental-hazard
places in 239 U.S. counties for three major environmental hazards: air
pollution, heat, and toxic sites. Subsequently we explore the extent to which
human mobility extends the reach of environmental hazards and also lead to the
emergence of latent exposure for populations living outside high hazard areas
with relatively considerable dwell time in high hazard areas. The findings help
quantify environmental hazard exposure more reliably, considering the role of
human mobility and activities. The interplay of spatial clustering in
high-hazard regions and human movement trends creates environmental hazard
traps intensifying exposure. Poor and ethnic minority residents
disproportionately face multiple types of environmental hazards, aggravating
potential health impacts. This data-driven evidence supports the severity of
these injustices. We also studied latent exposure arising from visits outside
residents' home areas, revealing millions population having 5% to10% of daily
activities occur in high-exposure zones. Despite living in perceived safe
areas, human mobility could expose millions of residents to different hazards.
These findings provide crucial insights for targeted policies to mitigate these
severe environmental injustices
