4.3.6. Human Health
Summary: Increases are likely in heat stress mortality (particularly in
Australia), tropical vector-borne diseases such as dengue, and urban pollution-related
respiratory problems. These impacts are small compared to the total burden of
ill-health, but they have the potential to cause significant community impact
and cost. Indigenous communities and economically disadvantaged persons appear
to be more at risk. Adaptation responses include strengthening existing public
health infrastructure and meeting the needs of vulnerable groups. A moderate
degree of vulnerability is apparent with health.
18.104.22.168. Health Impacts
Average life expectancy in Australia and New Zealand is relatively high, and
access to medical care is relatively good by international standards. There
are considerable inequalities in health status and access to services, however.
Disadvantaged groups such as indigenous peoples and the poor are likely to be
most at risk from the effects of climate change.
In parts of urban Australia, the frequency of very hot days (over 40°C) is
expected to increase by 50-100% for a 2°C increase in mean temperature (Hennessy
and Pittock, 1995). This is likely to lead to an increase in deaths, especially
in cities such as Melbourne that are subject to wide variability in temperature,
but insufficient information is available at present to quantify this impact.
There may be fewer deaths in winter with warmer temperatures. For example, the
winter excess in coronary heart disease mortality in Australia and New Zealand
appears to be related in part to ambient temperature (Enquselassie et al., 1993).
However, studies in other parts of the world suggest that reduced mortality
from cold extremes would probably only partly offset the heat stress effect
(IPCC 1996, WG II, Section 18.2.1).
In both Australia and New Zealand, there are significant food- and waterborne
diseases that occur more commonly in warmer conditions (IPCC 1996, WG II, Section
18.3.5). For example, in parts of Australia, an amoeba that causes meningoencephalitis
proliferates in water pipes that are heated in summer as the water travels overland
(IPCC 1996, WG II, Section 18.3.2). Hotter weather also will exacerbate urban
air pollution due to photochemical oxidants (Woodward et al., 1995), possibly
leading in the major cities (Sydney, Melbourne, Auckland) to increased frequency
of respiratory problems and deaths (IPCC 1996, WG II, Section 18.3.5). Australia
and New Zealand have rates of asthma and other allergic conditions that are
higher than elsewhere in the Pacific or in many parts of Europe, and these diseases
may be exacerbated by warmer and more humid climates (Pearce et al., 1993).
Any increase in extreme events and flooding, including those associated with
sea-level rise, would increase deaths, injury, infectious diseases, and psychological
disorders and may increase road accidents. Other waterborne illnesses-such as
viral, bacterial, and protozoal diarrhoea and cyanobacterial poisoning-would
be affected by any changes in water availability (due to flooding, droughts,
and public water shortages). Some disease vectors also are influenced by changes
in water availability. New Zealand currently is free of human arbovirus infections
(i.e., viruses borne by arthropods-ticks, mites, etc.), but if temperature and
rainfall alter it may become susceptible to infections that currently are common
in Australia (Weinstein et al., 1995). Vectors for dengue and malaria already
exist in Australia, and southward expansion of the vector populations with temperature
increases would increase the potential for insect-borne diseases to become more
widely established. These diseases are very sensitive to climate variability-for
example, outbreaks of dengue are much more common in the western Pacific islands
during relatively warm and wet La Niņa years (Hales et al., 1996).
Conditions forecast under climate change could alter the distribution and proliferation
of arthropod vectors and/or natural vertebrate hosts. Warmer and wetter conditions
would lead to increased incidences of insect-borne infections such as Japanese
Encephalitis virus, Murray Valley Encephalitis virus, Ross River virus, and
dengue. In southeastern Australia, epidemics of Murray Valley Encephalitis and
Ross River virus infection follow heavy rain in the Murray-Darling basin (Nicholls,
1986; IPCC 1996, WG II, Section 22.214.171.124), so additional cases might be expected
if the frequency or duration of heavy rainfall events increased. However, the
relationship between climate, vector distribution, and disease are complex.
For example, although the incidence of infection with Ross River virus may increase
with increased rainfall, the incidence of symptomatic disease may actually fall
because individuals who are infected as children remain asymptomatic and are
immune for life.
The indigenous peoples of Australia and New Zealand-Australian Aborigines,
Torres Strait Islanders, and Maori-may be more vulnerable to climate change
because their health status in general is worse than for other Australians (Australian
Bureau of Statistics, 1997) and other New Zealanders (Pomare et al., 1995).
These health status differences result largely from social and economic disadvantage,
which itself is a cause for susceptibility. For example, many Australian Aborigines
live in remote areas, in poor housing, and are particularly susceptible to infections
related to deficiencies in water supply and sewage disposal (Moss, 1994). Under
some scenarios, these conditions could worsen due to higher temperatures, changes
in rainfall, higher water tables, and rising sea levels. Reduced freshwater
supply, increased standing water, or both could increase exposure to microbial
and viral infections and vector-borne diseases (Kolsky, 1993; Hales et al.,
1995; Henderson et al., 1995; Jacobson and Graham, 1996).
The health impacts of climate change will include economic and social costs.
These costs are difficult to quantify, but the evidence suggests that the health
impacts for the region are likely to be relatively small compared to impacts
from other diseases and sources of mortality. At the same time, it should be
cautioned that there is considerable uncertainty in our current knowledge of
not only the likely direct impacts but also the complexities of social responses
to change and interaction with other sectors. For example, there could be changes
in the incidence of zoonoses (vertebrate animal-mediated diseases) such as leptospirosis,
a concern in New Zealand, as farming systems and zoonoses transmission alter
in response to climate change. Heat stress impacts will be affected by housing
choices and changing attitudes to air conditioning. More difficult to estimate
precisely-but possibly of greater importance to public health in the long term-are
the indirect effects of climate change, such as any adverse social and economic
effects, especially on vulnerable groups, arising from impacts on other sectors
and any large population shifts of "environmental refugees" (for example, from
Pacific atolls) (Moore and Smith, 1996).
126.96.36.199. Adaptation and Vulnerability
Major adaptation responses include strengthening the existing public health
infrastructure (such as disease monitoring, vector management, and primary health
care); improving protective systems where deficiencies are apparent already
(for example, comprehensive infectious disease surveillance and border quarantine
controls to reduce introduction of exotic pathogens); and meeting the needs
of the most vulnerable groups in the population who will be at greatest risk
from new climate-related threats to health (Woodward, 1996), including through
improvements in water supply and sewerage systems (Moss, 1994). Adaptations
to deal with the indirect socioeconomic effects arising in other sectors may
require significant policy responses at the national and international levels.