air pollution and health protection: why control pm and nowhy … · 2018. 11. 27. · • this is...

WORKING FOR A HEALTHY FUTURE

Air pollution and health protection:Why control PM and NO ?Why control PM and NO2?

Fintan [email protected]

Some personal observations

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Air pollution episodes – London smogs

• Very high levels of PM (Black Smoke) and SO2

• Health effects• Increased mortality and morbidity in immediately following days• Health effects were obvious: causality accepted (though detailed y p ( g

mechanisms unknown)

• Policy response• Policy response• Control the peaks / Eliminate the episodes: domestic coal burning• Largely successful • Problem solved?

22/06/2010IAPSC London 2

Daily variations at ‘normal’ levels

• Late 1980s and early 1990s: Time series studies linking daily pollution (typically 24-hr average) with numbers of death and hospital(typically 24 hr average) with numbers of death and hospital admissions in large cities

• Numerous well-conducted studies (North America, Europe, elsewhere) h d t ti ti ll i ifi t i tishowed statistically significant associations

• PM10 especially, also O3, NO2, SO2, CO…

• Nevertheless causality contested:Nevertheless causality contested: • Biological mechanisms were unclear – better understood now• Advanced statistical methods used

• COMEAP (1995): Imprudent not to consider PM10 effects as causal


Daily variations – policy implications

• Public health significance unclear / contestedTh t i k f li d th b li d t b l ith i ti• Those at risk of earlier death believed to be people with pre-existing serious cardio-respiratory disease

• Do all earlier deaths matter equally? What about years of life lost?

• Policy implications – control peaks or average exposure? Health effects occurred not just on high pollution days remove the• Health effects occurred not just on high-pollution days – remove the high pollution days and relationships practically unchanged

• No evidence of a threshold

• Control annual average PM10

• EPAQS (1995): Control both high days and annual average


The key issue: Long-term exposure and mortalitymortality

• Differences between cities with different average pollution levels, adjusting for other factorsadjusting for other factors• Early studies (e.g. 1970s, 1980s) could not adjust convincingly for other

factors

T j US h t t di• Two major US cohort studies • Six-Cities – Dockery et al., 1993• American Cancer Society (ACS) – Pope et al., 1995

• Main relationships in PM2.5; Implied much higher public health effects than from time series (‘daily variations’)

N id f th h ld• No evidence of threshold• WHO AQ Guidelines – not a standard, rather benefits of a reduction

• Causality contested – now widely accepted


Causality contested now widely accepted

PM2.5 (µg.m-3) and mortality, Pope et al (2002):Shape of the relationshipShape of the relationship

A] All cause mortality B] Cardiopulmonary mortality

Log Relative Risk and CIs of mortality 1982-1998 and

% C

I)

0.20.1

0-0.1-0 2 annual average

ambient particles (PM2.5 in µg.m-3) in 51 US metropolitanC] Lung cancer mortality D] All other cause mortalityR

isk

(90%

-0.2-0.3-0.4

51 US metropolitan areas, based on a cohort of 319,000 adults aged 30+

C] Lung cancer mortality D] All other cause mortality

g R

elat

ive

0.20.1

0-0.1

10 15 20 10 15 20

Log 0.1

-0.2-0.3-0.4


10 15 20 10 15 20

Quantifying health benefits of pollution control


Quantifying health impacts of the air pollution mixture: what about the other gases?mixture: what about the other gases?• CAFE (and other major Health Impact Assessments)

quantify relationships of health with PM and Oquantify relationships of health with PM and O3• Treat PM and O3 effects as additive • WHO: On current evidence, quantify all PM2.5 as equally harmful

• In this simplified model, what about the other gases?SO NO f bi PM• SO2, NO2 are precursors of ambient PM

• NO2 is also a precursor of ozone

• SO2 and sulphates – markers of industrial pollution• NO2, CO, PM number, nitrates – markers of traffic


Health Effects quantified in CAFE CBA and by COMEAP PM and ozoneby COMEAP – PM and ozone

• Chronic (long-term) exposure to particulate matter (PM):• Mortality (PM) and adults – the dominant effect;y ( ) ;• Infant mortality and PM• Development of bronchitis (PM)

• Acute (short-term) exposure to PM and to O3• Mortality (O3) – mortality and PM already included• Hospital admissions

R i t (PM O ) C di l (PM)• Respiratory (PM, O3); Cardiovascular (PM)• Days of Restricted Activity; Days off Work (PM, O3)• Days with symptoms and/or using medication (PM, O3)

• In people with chronic lung disease (asthma COPD)• In people with chronic lung disease (asthma, COPD)• In the general population

• Full CAFE CBA Methodology report (Hurley et al 2005) on the Web


Full CAFE CBA Methodology report (Hurley et al., 2005) on the Web

Mortality and PM2.5 compared with other risks

Gain (days) in life expectancy for a birth cohort

Effect Impact Male Female

Gain (days) in life expectancy for a birth cohort

10 µg.m-3 reduction in PM2.56% all-cause reduction (ages 30+)(Cardio-respiratory and Lung Ca) 222 218

Eli i t M t V hi lEliminate Motor VehicleTraffic Accidents (MVTA) Set MVTA hazard = 0 81 30

Eliminate passive smoking Reduce Lung Ca and CV hazards by 88 62Eliminate passive smoking g y10.5% (ages 20-64), 3.2% (ages 65+) 88 62


Commission’s proposals for ambient PM –reduce annual average PMreduce annual average PM2.5

• Focus on PM2.5 rather than PM10

• 20% reduction in PM2.5, by the year • Target, i.e. not legally binding

• A ‘cap’ of 25 µg/m3 PM2.5• Roughly equivalent to 40 µg/m3 PM10

• Legally binding

• Changes to ‘anthropological PM10’


CAFE CBA: estimated costs and benefits

• Current levels of PM2.5 air pollution imply loss of life t f b t 8 th thexpectancy of about 8 months, on average across the

EU-25

• Both costs and benefits increase as PM is reduced• Both costs and benefits increase as PM2.5 is reduced

• In monetary terms, benefits 5-20 times greater thancosts for a 20% reduction in PMcosts for a 20% reduction in PM2.5

• There is a strong economic case for even strongerreductions i e Europe wide the benefits of furtherreductions i.e. Europe-wide, the benefits of furtherreductions are 1-3 times greater than costs


Health benefits of controlling NO2


Direct effects of NO2 within the mixture

• Control of NO2 peaks – Yes (WHO Air Quality Guidelines)

• Control of ‘ordinary’ concentrations of NO2, expressed as annual average• Long-term exposure and adult mortality

• No effect in the ACS study; Yes in the Dutch NLCS-AIR and some other cohorts (especially of traffic-related pollution); B t i th l ti hi ith NO l ‘j t’ i di t f t ffi• But is the relationship with NO2 causal, or ‘just’ an indicator of traffic-related pollution?

• COMEAP (2009a) did not recommend direct quantificationNO d th i t h lth f hild COMEAP (2009b)• NO2 and the respiratory health of children: COMEAP (2009b)• Effects not clear enough to be quantifiable• NO2 unlikely to be dominant pollutant but a small NO2 effect cannot be

ruled out


ruled out

Outdoor NO2 and health: why control annual average NO ?average NO2?

• Two other principal possible reasons

• NO2 is a marker of the air pollution mixture from traffic and so controlling NO2 means controlling traffic pollution – or does it? • It used to be that reducing NO2 implies reducing the transport mixture as a

whole• But now NO2 can be controlled without controlling the mixture as a whole…

• Indirect effects of NO2, as precursor to nitrates and O3

• These indirect effects can be substantial, assuming the toxicity of nitrate PM is the same as that of the PM mixture of the same size


Evaluation of Air Quality Strategy in UK

• Study looked at a whole range y gof measures to reduce pollution based on various EU policies that affected emissions from:• Road transport• Electricity Supply Industry

• For road transport, greatest reductions were in primary PM, then nitrate PM, (then sulphates)

• NO2 reductions can have substantial health benefits

• Less if nitrates are less harmful


Conclusions

• There is very strong, quantifiable, evidence linking exposure to PM with increased risks of death, hospital admissions, symptoms, and other effects • The dominant impact is the effect on cardio-respiratory mortality of long-term

exposure to air pollution expressed as PM2.5. • This is a bigger public health issue than passive smoking or motor vehicle gg p p g

accidents • EU-wide, the estimated benefits of reducing annual average PM2.5 far outweigh

the estimated costs. There is an ongoing public health need for strong control

• While NO2 also causes damage to health, the direct benefits to public health from control of annual average NO2 are not easily quantified, and may be small. • There are indirect benefits, via control of nitrate PM and ozone. These indirect

benefits can be substantial.• It seems that, from a public health viewpoint, control of annual average NO2 is

best seen as part of a strategy to control PM2.5 and ozone, rather than as an d i it lf


end in itself.

air pollution and health protection: why control pm and nowhy … · 2018. 11. 27. · • this is...

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