Geography Reference
In-Depth Information
13.5.3
Natural or Physical Environments
Behind these first four domains of health factors are four categories of environmen-
tal determinants, related to the natural, built, economic and social environments. Al-
though the causes of disability and premature mortality often relate to one or more
of these factors, a WHO survey of the environmental effect on ill-health (Prss-
ￜstn and Corvel￡n
2006
) estimated that 24 % of the global disease burden (health
years lost) and 23 % of the annual deaths are due to what are described as 'modifi-
able environmental factors', proportions that rise to closer to a third for children.
These are described as the factors in the physical and built-environments that can be
altered; they exclude factors such as disease vectors in water bodies, impregnated
bed nets, as well as social behaviours or life-styles. The WHO report showed that
the burden of environmental effects on premature mortality and ill-health is far
higher in the developing countries and varies with disease type. Studies of the risk
factors of different diseases show that 85 out of the 102 types covered had an envi-
ronmental factor, although these varied considerably. The highest mortality propor-
tions were seen with diarrhoea (94 %) and malaria (42 %), far higher than the 20 %
from lower respiratory causes, although this rises to over 40 % in developing areas,
primarily due to fumes from the use of solid fuel fires in enclosed spaces. The risk
factor may be greater than previously thought, as recent work is showing that envi-
ronmental effects can be passed through generations through epigenetic processes
whereby genes are turned on or off (Tollefsbol
2014
).
The first of these environmental influences are those from the physical condi-
tions, features often forgotten when the focus of attention is upon cities in the devel-
oped mid-latitude world that have less extreme environments. For example, health
is often affected by extreme deviations from the normal
climatic regimes
, such as in
cases of extreme cold or heat and high humidity, where the elderly, young and those
in ill-health, die in larger numbers in such weather conditions. Some of these prob-
lems are made worse because of the heat-island effect of all the concrete, steel and
bricks in cities. For example, in July 1995 a Chicago heat wave led to temperatures
reaching over 40 ﾰC—although the effective temperatures as felt by the body in the
sun and in buildings were far higher—resulting in the deaths of over 600 people
(Klinenburg
2002
). The size of the mortality from this event in one city is worth
comparing with other statistics. In the decade after 1992, 2190 Americans died from
heat-related causes compared to 880 from floods and 150 from hurricanes. Although
this shows that extreme heat can result in spikes of mortality, it is important not to
underestimate the effect of disasters from
natural hazards
when many thousands,
even millions, of people have been killed by major storms, earthquakes, volcanic
eruptions as described in Chap. 8.
The second health effect of the physical environmental comes from various
bi-
otic hazards
, ranging from snakes to toxic plants, although these are often less of a
problem in cities as they are often deliberately eradicated. Of greater significance
are the diseases spread by contagion in a densely populated area by pathogens de-
veloped in, or carried by, various animals or insects. Perhaps the best known his-
toric examples come from the various plagues, such as the Black Death plague that
