This section is authored by Alistair Boxall, University of York Introduction
England is changing: over the next century alterations are predicted in climate, land- use, demographics, physico-chemical properties of the environment (for example acidification), water availability and the degree of urbanisation. Global climate
change (GCC), for example, is predicted to result in different weather characteristics in England. The English population is projected to continue growing, reaching over 63 million by 2039.38 The population is also getting older, births are continuing to outnumber deaths and immigration continues to outnumber emigration.38
All of these changes are likely to affect the risks from chemicals and other pollutants in the natural environment to human health by altering:
a) the types and quantities of chemicals that are released to, or formed in, the environment;
b) transport, accumulation and fate of chemicals in the environment; c) sensitivity of humans to a particular contaminant;
d) human behaviour (for example Figure 4.1)
Below we discuss some of these potential changes in exposure and risks, focusing mainly on GCC-drivers which is where most work has been done.
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Figure 4.1 Potential global climate change (GCC) related and other drivers that will affect the risks of pollutants to human health in the UK in the future
Source Adapted from Boxall et al.
Future changes in climate will impact chemical usage patterns and the amounts used, as well as how chemicals are formed in the natural environment and even alter exposure to existing chemicals. For example:
• For pesticides, biocides and pharmaceuticals, use will likely increase due to
changing disease and pest pressures (in addition to increases due to demographic changes).39,40
• As the generation of many natural toxins (for example algal, fungal and phyto-
toxins) is partly governed by temperature and moisture, GCC will affect the rates of formation of these substances in the environment as well as their geographical distribution.
• For legacy contaminants, such as mercury, that have been released into the
environment in the past and reside in soil and sediments, GCC may alter the environment in such a way that the contaminant can be released more rapidly.41 As well as the direct impacts of GCC on pollutants (more below), our response will also have impacts on other pollutants. For some chemical contaminants there may be a reduction in emissions to the environment. As many fossil-fuel combustion processes that generate greenhouse gases also emit other harmful air pollutants, decreases in fossil fuel use, resulting from greenhouse gas mitigation policies, will reduce ground-level air pollution by particulate matter and ozone in urban areas.41 Conversely, shifts to some types of biofuels may increase levels of air pollution in rural areas.
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GCC and pollutant pathways
Transport pathways for chemicals will be affected by changes in climate conditions which will affect human exposure.42 Aerial transport of chemicals, for example, is dependent on the surface temperature, air temperature and wind speed, all of which are predicted to change as a result of climate change. Increases in temperature resulting from GCC will result in increased volatilisation: this will increase long-range transport of persistent organic chemicals, such as PCBs and dioxins, and local bystander exposure to chemicals such as pesticides.41 Increases in the occurrence of extreme weather events, such as floods and droughts will alter the mobility of contaminants, providing pathways by which chemicals can move from contaminated areas such as contaminated land sites and sediments to uncontaminated areas. On the land, alterations in soil characteristics such as reductions in soil organic carbon content, increases in dustiness and changes in soil hydrology will alter how contaminants are sequestered in soil systems and transported around rural
catchments.39 The dilution potential of contaminants in rivers and streams in the UK will also change.43 In agricultural areas, changes in irrigation practices and more reliance on re-use of wastewater, in response to GCC, could also move
contaminants from waterbodies and sewer systems onto land.
GCC and pollutant fate
As well as affecting environmental transport processes, GCC will also alter the fate of chemicals. Increases in temperature and changes in moisture content are likely to alter the persistence of chemicals.43 Biodegradation is generally faster at higher temperatures and moisture contents, so faster degradation of organic chemicals would be expected in hotter and wetter regions. Rates of photolysis are also expected to increase in some regions due to reduced cloud cover meaning that photosensitive chemicals will be exposed to higher intensities of UV light. All of these different changes in fate and transport can have both positive and negative
implications for contamination of air, surface waters, soils, food and drinking water supplies and air and hence human exposure. The relative changes in exposure will likely vary depending on region and the physico-chemical properties of the chemical itself.
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Human vulnerability
Human vulnerability to pollutant exposure will be altered.44 Heat makes humans more vulnerable to adverse effects of air pollutants, such as ozone and PM10, so anticipated temperature increases under GCC could increase sensitivity to aerial contaminants. Chemical exposure may also make humans more vulnerable to GCC- driven changes, for example impairment of the human immune system resulting from chemical exposure could increase vulnerability to vector-borne diseases which are predicted to increase under GCC. Human behaviour will also be affected by GCC and this will have implications for exposure.
Impacts of future change on the health risks of Pollutants - Summary
Overall, human exposure and sensitivity to pollutants will be altered in the future. In some instances, these alterations will have a positive impact on exposure and health while in others health impacts may be exacerbated. We therefore urgently need to establish how exposures of pollutants of potential concern could change under different future scenarios and to use the results of such analyses to identify potential interventions to reduce the health impacts.
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Box 3 Pollution and the weather
Dr Matthew Hort, Head of Atmosphere, Met Office
The gases and particulates that make up ‘air pollution’ originate from sources as diverse as transport, industry, agriculture and the natural environment. These sources are also spread out geographically across our cities, countries and the world. Pollution though does not stay located at its source, as once in the atmosphere it is blown, mixed, diluted, removed and reacts with, amongst other things, the wind, humidity, clouds, rain and other chemical compounds.
The weather we experience knows no borders and the winds, systems, and storms evolve, grow and diminish perpetually in a continuum spanning from the local street to the world. Therefore, chemicals and particulates once in the atmosphere can potentially also be transported over distances ranging from a few millimetres to 1000s in km. The transport by the atmosphere also brings together and enables interactions and reactions of and between the gases and particulates. While this is a universal phenomenon it can perhaps be appreciated more easily when we think about specific events: The eruption of the Icelandic volcano in 2014 that resulted in volcanic gases, including Sulphur Dioxide which then created sulphate particles, spreading across Northern Europe; the presence of fine sand from the Sahara on our cars that has been blown all the way from North Africa before being removed from the atmosphere by rain; the intermittent smell of a domestic wood fire on the street or in our gardens; and of course, the clear increase in traffic ‘fumes’ as we approach major roads and junctions.
This means that the causes of air pollution at a specific location can be: predominantly located far away; be an even mix of near and far sources or be predominantly due to local emitters. Even in our cities, while the pollution can be dominated by local traffic emissions it still contains, often significant, elements from sources across the rest of the country, shipping in the surrounding waters, the wider continent and also the rest of the northern hemisphere. As such, while it is often correct to focus on local sources for local effects, it is however wrong to do this to the exclusion of considering the contribution and impact from the wider geographical area. The meteorology and dispersion after all follow the rules of physics and chemistry rather than administrative or societal boundaries.
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