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5 Methodology – Air pollution health effects

The methodology required for quantifying the health effects of air pollution is derived from the Health and Air Pollution in NZ (HAPiNZ) study, a joint initiative from the Health Research Council, the Ministry for the Environment and the Ministry of Transport (Fisher et al, 2007). This study represents the most comprehensive analysis of air pollution, its health implications, and the resulting societal costs conducted in New Zealand. The research evaluated the effects of specific source categories of emissions from vehicles (including private petrol cars, diesel cars, and diesel trucks), industry, domestic and total sources in New Zealand.

The research encompassed five interconnected components:

  • air quality, meteorology and emissions data analysis

  • air pollution exposure assessment

  • health impact assessment

  • economic impact assessment

  • preventative policy assessment.

A more detailed explanation of the methodology can be found in the HAPiNZ report. Tables 5.1, 5.2 and 5.3 summarise the health effects of air pollution from domestic, transport, and industrial sources, respectively.

Table 5.1: Annual health effects associated with domestic sources, including from particulate matter (PM10) and carbon monoxide (CO)

View the annual health effects associated with domestic sources, including from particulate matter (PM10) and carbon monoxide (CO) (large table).

Table 5.2: Annual health effects associated with transport sources, including from particulate matter (PM10) and carbon monoxide (CO)

View the annual health effects associated with transport sources, including from particulate matter (PM10) and carbon monoxide (CO) (large table).

Table 5.3: Annual health effects associated with industry, including from particulate matter (PM10) and carbon monoxide (CO)

View annual health effects associated with industry, including from particulate matter (PM10) and carbon monoxide (CO) (large table).

Monetary estimates of the air quality benefits are based on the assumptions made in the HAPiNZ study, which was based on previous research in New Zealand (described in detail in Fisher et al, 2007), and results from overseas studies adjusted for New Zealand conditions. Table 5.4 gives a summary of the specific health effects and their cost per case as was used in the HAPiNZ study. These are not personal costs, but costs to the NZ economy – the external costs of air pollution.

Table 5.4: Summary of costs of events used in the analysis

Effect

Cost per unit

Mortality

$750,000

Bronchitis

$75,000

Other admission (respiratory)

$2,700

Other admission (cardiovascular)

$3,675

Cancer

$750,000

Restricted activity day

$92

These figures have a degree of subjectivity, and are estimates only. There is no international agreement on how to apply economic analysis – and the values used in various countries can differ widely. For instance the premature mortality is argued to be as low as $50,000 to as high as $6,000,000, with the New Zealand Ministry of Transport adopting $2,700,000 for road crash death costs. The figures used here are reasonably conservative estimates, calculated for New Zealand circumstances. Different studies may apply different costs. In addition, there are some effects that are not studied, nor explicitly costed, mainly because the research results are not available. These include asthma cases, short-term effects, and toxic effects. Similarly some effects will incur additional costs that are difficult to quantify, including costs of extra doctors visits and medication, lower-level effects due to mild but perhaps widespread effects from drowsiness, headaches, loss of attention, and quality of life that may not be included in the restricted activity day analysis. Finally the general economic effect of perceptions of ‘poor air quality’ on tourism and recreation are not negligible, although beyond the scope of this study.

5.1 Air pollution health effects summary

The total costs of health effects of air pollution can be estimated from the health effect and the cost per case of that effect, shown in Table 5.5. The largest component of the ‘economic health burden’ is the loss of life-years as a result of premature mortality, followed by restricted activity days, and then chronic bronchitis.

Table 5.5: Summary valuation of annual health effects in New Zealand due to domestic, industrial and transportation related air pollution ($ million)

Effect

Domestic

Vehicle

Industrial

Total

Mortality (due to PM10, NO2)

267.0

310.5

98.3

675.8

Mortality (due to CO)

52.5

64.5

16.5

133.5

Bronchitis and related

66.5

40.6

8.7

115.8

Respiratory/cardiac admissions

1.2

0.7

0.2

2.1

Cancer

14.3

16.5

4.5

35.3

Restricted-activity days

101.7

61.7

13.3

176.7

Total

503.2

494.6

141.5

1,139.2

These costs are used to make a basic comparison with the greenhouse costs, although there remains a high degree of subjectivity in determining these costs (as with the greenhouse gas costs).