Urban Heat Impact (UHI)s have the
potential to directly influence the health and welfare of urban residents.
Within the United States alone, an average of 1,000 people dies
each year due to extreme heat. As
UHIs are characterized by increased temperature, they can potentially increase
the magnitude and duration of heat
waves within cities. Research has
found that the mortality rate during a heat wave increases exponentially with
the maximum temperature an effect
that is exacerbated by the UHI. The night-time effect of UHIs can be
particularly harmful during a heat wave, as it deprives urban residents of the
cool relief found in rural areas during the night.
Research
in the United States suggests that the relationship between extreme temperature
and mortality varies by location. Heat is more likely to increase the risk of
mortality in cities at mid-latitudes and high latitudes with significant annual
temperature variation. For example, when Chicago and New
York experience unusually hot
summertime temperatures, elevated levels of illness and death are predicted. In
contrast, parts of the country that is mild to hot year-round have a lower
public health risk from excessive heat. Increased temperatures and sunny days
help lead to the formation of low-level ozone from volatile organic compounds
and nitrous oxides which already exist in the air. As urban heat islands lead
to increased temperatures within cities, they contribute to worsened air
quality.
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