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Chapter 14: Global Change, Air Quality, and Human Health

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1 Chapter 14: Global Change, Air Quality, and Human Health
Protecting our Health from Professionals Climate Change: a Training Course for Public Health Chapter 14: Global Change, Air Quality, and Human Health Air quality and climate change are intimately linked. This lecture will examine those linkages and their implications for public health.

2 Lecture Overview Introduction to climate and air quality
Characteristics and health effects of major anthropogenic air pollutants Exposure-response relationships Global burden of disease due to air pollution Has climate change affected air pollution? Observed trends Integrated modeling Co-benefits assessment We will cover these topics. “First,… then,… then,… finally”

3 Introduction The mixtures of air pollutants produced by burning of fuels can: Adversely affect human health Promote climate change In addition Climate change can influence air pollution, resulting in direct health effects Climate change can affect other aspects of air quality, including smoke from agricultural or wildfires, and aero-allergens like pollen and mold spores In relation to first main bullet: Fuel combustion is responsible for most of the air pollutants which adversely affect human health. Similarly, most anthropogenic climate change is due to fuel combustion. So human health and climate change are inextricably linked at the level of emissions sources of air pollution. The picture of course is more complicated in that pollutants emitted by fuel combustion affect health and climate to varying degrees and even in different directions, but we’ll leave those complications for later… This linkage between health and climate impacts of fuel combustion implies co-benefits of mitigation… more later on that too. In relation to second main bullet: In addition, weather and climate can influence air quality in a variety of ways. Horizontal and vertical air motions in the atmosphere transport and dilute air pollutants emitted by human activities. Temperature, humidity, rainfall, and winds also may influence the generation of some unwanted air contaminants, including smoke from wildfires and allergenic pollens. STRATUS CONSULTING

4 London: Mid-day in December 1952
This is a photograph taken at mid-day on the streets of London, during the famous December 1952 pollution episode. Witnesses reported that the smoke was so thick, it was hard to see across the street. This episode made clear to the public and policy makers that air pollution can be deadly… UK Met Office, 2009

5 London Killer Fog, December, 1952
Here are the basic data from the 1952 London episode. Over five days in early December, a stagnant air weather pattern sat over London. In other words, there was little or no horizontal or vertical air motion. As a result, all of the smoke emitted by residential coal stoves and industrial sources in the city, stayed near the ground and was not dispersed, leading to very high smoke concentrations. Corresponding in time to the rise in smoke levels, death counts also rose to very high levels, and did not return to normal levels for several weeks. It has been estimated that between 4000 and 10,000 excess deaths occurred as a result of this air pollution episode. And it didn’t take fancy statistical methods to tease out this result. This episode, and others like it in the U.S. led to the development of air quality regulations by the 1960s which over time have led to major improvements in air quality in the U.S. and Europe. Even so, by using the sophisticated methods of modern epidemiology and biostatistics, health effects can still be seen. UK Met Office, 2009 Date

6 PM2.5 Levels in Dhaka, Bangladesh
Standard This graph reminds us that air quality remains a serious problem in the cities of the developing world. Red line indicates the Bangladesh 24 hour PM2.5 standard. Clean Air Initiative, 2006

7 Common Pollutants that are of Human Health Concern
Carbon monoxide (CO) Nitrogen dioxide (NO2) Lead (Pb) Sulfur dioxide (SO2) Ozone (O3) Particulate matter (PM2.5,PM10) Let’s now turn our attention to the human health effects of air pollution. We begin by considering a handful of common pollutants that are seen in most urban areas. These six pollutants have been the focus of most air quality regulations at the national level. In the US, they are called “criteria pollutants.” Aside from lead, which historically was a petroleum fuel additive, these pollutants tend to occur wherever fuel combustion takes place. In urban areas, concentrations in the air often reach unhealthy levels. In the developed world, emissions controls and other technological innovations have reduced CO, NO2, Pb and SO2 concentrations markedly since the 1960s. However, some of these pollutants remain serious challenges in many developing world cities. However, Ozone and PM remain serious concerns in both developing and developed countries. We will consider these two pollutants in greater detail.

8 Carbon Monoxide Produced by incomplete combustion
Inhibits the capacity of blood to carry oxygen to organs and tissues. People with chronic heart disease may experience chest pain when CO levels are high At very high levels, CO impairs vision, manual dexterity and learning ability, and can be fatal Read through bullets

9 Nitrogen Dioxide Is produced from high-temperature combustion
Affects lung function in persons with asthma Contributes to acid rain and secondary particle formation Is a precursor of ground-level ozone Read through bullets

10 Lead Retards intellectual development of children
Lead in gasoline was historically the principal source Read through bullets

11 Sulfur Dioxide Emitted from combustion of sulfur-containing coal and oil, and from metal smelting operations Reversible declines in lung function of people with asthma, and exacerbates respiratory symptoms in sensitive individuals Also contributes to acid rain and to formation of PM2.5 through atmospheric reactions Emissions reduced using scrubbers Read through bullets

12 Ozone Main pollutant responsible for photochemical smog, formed via reactions in the atmosphere from primary pollutants (NOx and VOCs) in the presence of sunlight Higher temperatures favor ozone formation Strong oxidant that damages cells lining the respiratory system, resulting in a variety of adverse health outcomes, including lung function decrease, asthma attacks, and premature death Ozone is also a greenhouse gas Ozone or O3 is a simple gas comprised of three oxygen atoms .Tropospheric or “ground level” ozone is a secondary pollutant, meaning that it is not directly emitted from a source, but rather forms via reactions in the atmosphere involving primary pollutants (nitrogen oxides and volatile organic compounds) and sunlight. Ozone mainly occurs in warm, sunny periods when formation is favored. Ozone is a strong oxidant which, upon inhalations, reacts with and damages the epithelial cells lining the respiratory system, from the nose down to the deepest parts of the lung where oxygen is absorbed. Cells in the deep lung are most vulnerable because they are not protected by a mucus layer. Ozone also is an important greenhouse pollutant which absorbs energy in the infrared spectrum.

13 Ground-level Ozone Formation
This slide shows a schematic description of tropospheric ozone formation in urban areas. Precursor gases emitted, mainly by fossil fuel combustion and evaporative emissions, react in the presence of sunlight to form ozone. Because these reactions take some time to play out, high ozone levels are often observed down-wind of the urban source areas, over broad regions. Queensland Government Environmental Protection Agency, 2006

14 Particulate Matter (PM2.5, PM10)
Can be either primary or secondary; produced by combustion, atmospheric reactions, and mechanical processes Wide range of physical/chemical properties Wide range of human health impacts, including premature death Higher temperatures may favor secondary formation Some particle types contribute to climate warming; others to climate cooling In contrast to ozone, which is a distinct chemical compound and a gas, particulate matter is a term that refers to any solid or liquid material suspended as small particles in air. [note: The numerical subscripts (e.g., 2.5 or 10) refer to the upper size limit for that definition. For example, PM2.5 includes all suspended particles that are smaller than 2.5 micrometers (one millionth of a meter) in aerodynamic diameter. The concept of aerodynamic diameter adjusts for the effects that particle density and shape have on the motion of particles in air. For a spherical water droplet, physical diameter equals aerodynamic diameter.] Particles can be directly emitted (primary) or can form through reactions in the atmosphere (secondary). Major physical processes of primary production include combustion of fuels and other organic matter, and mechanical processes like wind and friction. Because PM can include any suspended solid or liquid material, the physical and chemical properties vary tremendously. Based largely on epidemiology studies, PM exposures have been linked to a wide range of human health effects, including premature deaths. Some secondary particles, such as sulfates, may form more rapidly at higher temperatures. Particles have complex impacts on the global radiation balance, with some having positive radiative forcing (e.g., black carbon), and others having negative radiative forcing (e.g., sulfates)

15 Fine Particle Composition
This slide shows an example of the complex nature of fine particulate matter. Note that in the Eastern U.S. site, sulfates make up the largest single fraction, followed by organic carbon compounds and a variety of other components. Annual average fine particle data for 2001 from the Look Rock station of the Tennessee Valley Authority Tennessee Valley Authority, 2009

16 Health Effects of Air Pollution
Historical experience provides strong evidence for causal relationship between air pollution and premature death Modern epidemiology studies have consistently found significant associations Two primary epidemiologic study designs: Time series studies of acute effects Cohort or cross-section studies of chronic effects Let’s look at the evidence for particle health effects… Let’s now dig a bit deeper into what is known about the human health effects of these pollutants. As an overview of the evidence… read slide.

17 Air Pollution Epidemiology
Provides results relevant for policy makers Assesses effects of real mix of pollutants on human health Includes full range of susceptible populations Read slide. Epidemiology is the most important tool by which public health scientists study the links between air pollution and adverse health impacts. It has important advantages but also limitations, as compared to laboratory experimental approaches.

18 Air Pollution Epidemiology (cont.)
But… Pollutants tend to co-vary, making it hard to identify pollutant-specific effects Demonstrates association between outcome and exposure, but not cause and effect Confounding factors must be controlled Exposure assessment is “ecologic” A confounder is a third variable, which is both a risk factor for the health outcome of interest, and also correlates with the air pollutant of interest. If not controlled, confounders can lead to biased associations between air pollution and health. Exposure assessment is a big challenge in air pollution epidemiology. A health study would ideally like to measure exposure levels for each person at risk in the population. But this is infeasible. In most study, the exposures of an entire urban area are represented by one or more monitoring sites. Ecologic in this sense means that data are only available at the group level. In many air pollution epidemiology studies, all data are ecologic.

19 Time Series Epidemiology
Addresses short-term, acute effects of air pollution Involves analysis of a series of daily observations of air pollution and health data Widely used and economical approach, often utilizing readily-available data Basically go through the bullets

20 Time Series Epidemiology (cont.)
Temporal studies avoid many of the confounding factors that can affect spatial studies However, time-varying factors may confound the pollution associations … Seasonal cycles, weather variables, day of week Basically go through the bullets

21 Ozone and Acute Deaths Bell et al., 2004
For example, here are some results on the acute mortality effects of ozone, from a large multi-year study in the US Bell et al., 2004

22 Acute Mortality Responses to PM in US, Europe, and Asia
Exposure Response Exposure Risks 0.46 0.62 0.5 0.1 0.2 0.3 0.4 0.6 0.7 US (90 Cities)* Eur (21 Studies)* Asia (6 Studies) Percent Increase 0.46 0.62 0.5 0.1 0.2 0.3 0.4 0.6 0.7 US (90 Cities)* Eur (21 Studies)* Asia (6 Studies) Percent Increase For acute mortality effects of PM10, this slide summarizes the magnitude of the exposure-response relationship in terms of the percentage increase mortality per microgram per cubic meter increase in the ambient concentration of PM10 (particulate matter less than 10 micrometers in diameter). For example, the value for the United States is equivalent to a finding that the estimated relative risk per microgram per cubic meter increase in ambient PM10 concentrations is More generally, the results for the different locations suggest that the impact of changes in ambient PM10 concentrations are similar in different continents. Huizenga et al., 2005

23 Prospective Cohort Studies
Address long-term, chronic effects Large populations in multiple cities enrolled and then followed for many years to determine disease or mortality experience Must control for “spatial” confounders, e.g., smoking, income, race, diet, occupation Assessment of confounders at individual level is an advantage over cross-sectional, “ecologic” studies The prospective cohort study design could be called the gold standard for air pollution epidemiology. Read characteristics. These studies tend to be very expensive and require many years for completion. Retrospective exposure assessment as in the American Cancer Society cohort study, can get around these constraints.

24 Results from Harvard Six Cities Study
Long-term average concentrations of fine particle air pollution were associated with mortality rates, controlling for individual-level risk factors across six US cities In a classic Harvard prospective cohort study, 8,000 people were studied for years in six small cities, which followed a pollution concentration gradient. As particle concentrations increased, there was an almost directly proportional increase in the death rate in the residents studied. The original study underwent a re-analysis, which included different statistical techniques and additional confounders — results were nearly identical. Cities from left to right: P=Portage, Wisconsin T=Topeka, Kansas W=Watertown, Massachusetts L=St. Louis, Missouri H=Kingston and Harriman, Tennessee S=Steubenville, Ohio Dockery et al., 1993

25 American Cancer Society Study
Pope, C.A. et al., Journal of the American Medical Association: 287, , 2002 The six cities study was followed by a larger, nationwide study in the US American Cancer Society (ACS) cohort. Results emerged just two years after the Six Cities study, in This was made possible because the cohort enrollment and follow up had already occurred. The “air pollution” analysis simply involved finding historical PM2.5 data from 50 of the ACS cities and then doing the data analysis. Source: Pope et al., 2002

26 American Cancer Society Cohort Study
Objective: To assess the relationship between long-term exposure to fine particulate air pollution and all-cause, lung cancer, and cardiopulmonary mortality Approach: Vital status and cause of death data were collected by the American Cancer Society through 1998 in 500,000 US adults from 50 urban areas for whom air pollution exposure data were available in 1980 This was a much larger study than the Six Cities study, both in number of cities and number of subjects.

27 American Cancer Society Study Results
This table, taken from the 2002 follow up paper by Pope and colleagues, shows the main results of the study, expressed as “relative risks” of mortality associated with a 10 microgram per cubic meter increase in PM2.5 concentrations. Essentially, these results quantify the differences in mortality risk across the 50 cities as a function of average air pollution concentrations. The relative risk quantifies the proportional increase in mortality for a given change in exposure. They give results here using three different exposure assessments. The first column gives RR results based on PM2.5 data collected around the time that the cohort was originally recruited. The second column gives RR results using more recent data on PM2.5. The final column gives RR using the average of the early and late PM2.5 concentrations. These latter data have been most widely applied in policy circles. For all cause mortality, there was a six percent increase in mortality risk for a 10 microgram per cubic meter increase in annual average PM2.5 concentrations. Pope et al., 2002

28 American Cancer Study Conclusion
“Long-term exposure to combustion-related fine particle air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality” Here is the key conclusion of the Pope et al., 2002 paper: Pope et al., 2002

29 WHO 2005 Air Quality Guidelines: Particulate Matter
PM2.5 PM10 10 μg/m3 annual mean 25 μg/m3 24-hour mean 20 μg/m3 annual mean 50 μg/m3 24-hour mean Based largely on the ACS study, supported by many other studies, the WHO in 2005 established PM2.5 air quality guidelines (AQGs). The 2005 AQG for particulate matter represented the first time a guideline value for particulate matter (PM) was established. As no threshold for PM has been identified below which no damage to health is observed, the recommended value should represent an acceptable and achievable objective to minimize health effects in the context of local constraints, capabilities and public health priorities. However, the aim should be to achieve the lowest concentrations possible in order to minimize adverse health impacts. The particles are identified according to their aerodynamic diameter, as either PM10 (particles with an aerodynamic diameter smaller than 10 µm) or PM2.5 (aerodynamic diameter smaller than 2.5 µm). The latter are more dangerous since, when inhaled, they may reach the peripheral regions of the bronchioles, and interfere with gas exchange inside the lungs. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer. In developing countries, exposure to pollutants from indoor combustion of solid fuels on open fires or traditional stoves increases the risk of acute lower respiratory infections and associated mortality among young children; indoor air pollution from solid fuel use is also a major risk factor for chronic obstructive pulmonary disease and lung cancer among adults. Different values exist for the annual AQG compared to the 24-hour value recognizing that combinations of events, some beyond our control such as weather, can help increase ambient concentrations for short periods of time. The significantly lower annual AQG value compared to the 24-hour value is an indication of the severity of the health impacts from particulate matter where a location that continuously avoids violating the 24-hour standard would likely to have an annual value that significantly exceeds the annual AQG indicating that ambient pollution in the location is having significant adverse impacts on the local population. World Health Organization, 2008d

30 WHO 2005 Air Quality Guidelines: Ozone
Ozone (O3) 100 μg/m3 8-hour mean Likewise, ozone air quality guidelines were updated. World Health Organization, 2008d

31 Average Ambient Air Quality Levels (2000-2003)
Notes: Busan ( ); Dhaka ( ); Hanoi ( ); Jakarta ( ); Kathmandu (2003); Manila – PM10 ( ); Mumbai ( ); New Delhi ( ); Osaka ( ); Seoul ( ), SPM ( ); Surabaya ( ) Tokyo ( ) Clean Air Initiative, 2004 3 But air quality remains a very serious challenge in many Asian cities, as shown on this summary slide giving average concentrations for key pollutants. Because it is not feasible to carry out large-scale epidemiology studies in every city, there is a need for methods to use published exposure response relationships, such as from the ACS study, along with local air quality levels, to estimate the burden of disease due to current air quality. SPM Limit = µg/m3 (WHO, 1979) SO2 Limit = 50 µg/m3 (WHO, 1999) SPM SO2 PM10 Limit = 50 µg/m3 (USEPA, 1997) NO2 Limit = 40 µg/m3 (WHO, 1999) PM10 NO2

32 Health Impact Assessment
Step 1. Model future environmental conditions under various emissions and/or climate scenarios Step 2. Gather existing knowledge regarding human health impacts given a change in environmental conditions (based on “exposure-response” equations) Step 3. Estimate health impacts of modeled environmental changes These epidemiology and other results have been very widely used in health impact assessments. Health impact assessment is a modeling strategy that is very useful in estimating how many people might be affected by assumed changes in environmental conditions, including air quality. In the context of climate change, the usual strategy for analysis is outlined here. Step 1 involves modeling Step 2 involves finding relevant epidemiology results expressed as “exposure-response” relationships Step 3 puts information from steps 1 and 2 together to calculate excess response given the modeled change in exposure

33 Exposure-Response Calculations
Excess deaths attributed to PM is estimated by: Where: ∆y is the change in mortality incidence y0 is the baseline mortality incidence, equal to the baseline incidence rate times the potentially affected population β is the effect estimate ΔPM is the change in PM2.5 For example, we can calculate the change in mortality incidence using an exposure-response model like this. Go through and define each term. We get beta from the RR results such as those in the Pope paper. The delta PM is the difference in PM concentration that we are interested in. Some examples of delta PM: 1) it be a change in PM in 2050 compared to 2010 resulting from emissions and climate changes, or 2) it could be the difference between observed PM in a city and the natural background level, The latter approach was used in the global burden of disease study to estimate how much global mortality is caused by PM levels in urban areas… STRATUS CONSULTING

34 Global Burden of Disease – WHO 2004
Here’s the main publication of that work. Cohen et al., 2004

35 Population Exposure to Particulate Matter
An econometric model was used to estimate PM10 in cities where no measurements existed. Only three cities in all of Africa had actual monitoring data, which means that estimates of PM10 there are likely to be highly uncertain. Cohen et al., 2004

36 Estimates of the Health Impact of Particulate Matter Exposure
These are the main results of the mortality estimates, split by region and for the whole world. Results are expressed both in units of deaths and in units of Disability Adjusted Life Years. Cohen et al., 2004

37 The Challenge for Air Pollution and Climate Change
Can we assess potential future health impacts of air quality changes resulting from global climate change? So we see that epidemiology studies have told us much about the human health risks of air pollution - especially for PM and ozone (data not shown). We also see that epidemiology findings can and have been used in health impact assessments. How might we apply this in the context of climate change? Let’s look at an example from the recent New York Climate and Health Study

38 Effects of Climate Change on Tropospheric Ozone Formation
Formation reactions for ozone happen faster at high temperatures and with greater sunlight Biogenic VOC emissions increase at higher temperatures Regional air mass patterns over time and space may change, altering stagnation and clearance events The mixing height of the lower atmosphere may change, affecting the dilution of pollution emitted at the surface The focus of the study was on how climate change could affect ozone, and how ozone in turn could affect mortality. This slide illustrates ways in which weather and climate can influence ozone concentrations near the ground. Read bullets.

39 The New York Climate and Health Project
Linking models for global and regional climate, land use and cover, and air quality… To examine the potential public health impacts of ozone under alternative scenarios of climate change and regional land use in the 2020s, 2050s, and 2080s in the New York City (NYC) metropolitan region The overall goal of New York Climate and Health Project is summarized here.

40 Approach Develop exposure-response function for ozone using historical data from the NYC metropolitan area Develop an integrated modeling system that includes modules for global climate, regional climate, and regional air quality Examine alternative greenhouse gas growth scenarios Combine scenarios to assess potential mortality risks in the NYC metro area in the 21st century The strategy for accomplishing this goal is outlined here. This is basically a health impact assessment.

41 Developing NYC Exposure-Response Functions for Temperature and Ozone
Outcome: All internal-cause daily deaths at county level (JJA: ) β coefficient estimates (Standard Errors) Input to risk assessment POISSON Regression Day of Week (Indicator Variable); Spline of time Predictor: Daily ozone from 16 stations Model Outputs We started with an epidemiologic analysis, using a daily time series study design. Here, we had ten years of daily data from the 31 county New York City (NYC) metropolitan areas. We used Poisson multiple regression analysis to estimate the slopes related both ozone and temperature to excess daily deaths, controlling for potential confounders. Walk through the variables from left to right. In the yellow boxes, we see the basic outputs which then become inputs to the impact/risk assessment. The final regression equation is shown at the bottom. PREDICTOR: Daily mean temp. from 16 stations Final Model: log (daily deaths)= DOW + spline(time) + b1(mean Tlag0)1-3 + b2(max O3 lag0-1)

42 Integrated Modeling System Diagram
In order to examine future ozone and heat levels in the region, we needed to relevant global and regional scale models. Note the components, moving from left to right.

43 Modeling Domains Global climate (4 x 5) Health impacts
A key goal was to take coarse-scale outputs from the global climate model, and “downscale” those results to a finer scale that corresponds more closely to relevant administrative boundaries, like counties. Regional climate and ozone (36 km)

44 Impact of Climate Change on Summertime Ozone Concentrations
Hogrefe et al., 2004 ∆2050s ∆2080s This figure shows the modeled ozone concentrations in the four decadal periods. The results for the 1990s are expressed as mean ozone concentrations during the June, July, August period from The subsequent decades show the CHANGE in concentrations in going from the 1990s to the relevant decade. We see that the model predicts a gradual increase in ozone concentrations across decades within the main modeling domain. These data are resolved to 36 by 36 km grid boxes over the modeling domain.

45 Impact of Climate Change on Compliance with Ozone Standards
Simulated changes in 8-hour standard exceedance days with climate change 1990s — 2020s If we look at extreme values, we see more striking changes. For example, this plot shows the change in the number of exceedance days in the 2020s vs. 1990s for a daily 8-hour maximum concentration of 80 ppb. Here we’ve interpolated the 36km grid to counties, in preparation for health impact assessment, since baseline mortality rates are available for counties.

46 Modeled Changes in: Mean 1-hr max O3 (ppb) O3-related deaths (%)
Focusing now on the 31 county NYC metropolitan area, here we estimate the percent change in mortality that might results from the project changes in ozone concentrations at the county level, in this case showing 2050s data vs. 1990s. Knowlton et al., 2004

47 Review The mixtures of air pollutants produced by burning of fuels can
Adversely affect human health Promote climate change In addition Climate change can influence air pollution, resulting in direct health effects Climate change can affect other aspects of air quality, including smoke from agricultural or wild fires, and aero-allergens like pollen and mold spores Fuel combustion is responsible for most, though not all, of the air pollutants which adversely affect human health. Similarly, most anthropogenic climate change is due to fuel combustion. So human health and climate change are inextricably linked at the level of emissions sources of air pollution. The picture of course is more complicated in that pollutants emitted by fuel combustion affect health and climate to varying degrees and even in different directions, but we’ll leave those complications for later… This linkage between health and climate impacts of fuel combustion implies co-benefits of mitigation… more later on that too. Finally, weather and climate can influence air quality in a variety of ways. STRATUS CONSULTING

48 Furthermore There are other “air pollutants” besides the ones which come out of tail pipes and smoke stacks which have important impacts on human health, and for which climate change is causing changes… Fuel combustion is responsible for most, though not all, of the air pollutants which adversely affect human health. Similarly, most anthropogenic climate change is due to fuel combustion. So human health and climate change are inextricably linked at the level of emissions sources of air pollution. The picture of course is more complicated in that pollutants emitted by fuel combustion affect health and climate to varying degrees and even in different directions, but we’ll leave those complications for later… This linkage between health and climate impacts of fuel combustion implies co-benefits of mitigation… more later on that too. Finally, weather and climate can influence air quality in a variety of ways. STRATUS CONSULTING

49 Forest Area Burned and Temperature Trends Canada 1920-1999: 5-year Means
Smoke from natural or man-made fires is another form of air pollution that can influence public health, as well as contribute to global warming. This slide shows data from a recent study that tracked forest fires in Canada from about 1920 to There was an increasing trend in forest area burned that coincided with observed and simulated temperature trends since about 1960. This upward trend likely resulted from global climate change, as warmer air resulted in decreased soil moisture and greater tendency for natural fires. Also, man-made fires may be harder to control as soil moisture decreases… Gillett et al., 2004

50 Start Date of Birch Pollen Season in Brussels 1970-2006 Days after Jan 1 (5-year running means)
Another aspect of air quality relates to the amount of allergenic particles (e.g., pollen and mold) present in the air. Trends in pollen seasons have been observed in recent decades. These data show the trend toward earlier birch tree pollen seasons in Brussels from 1970 through This is likely due to warmer temperatures that result in earlier flowering in the spring. The health implications of these changes have not been documented extensively. In particular, it is unclear whether the total amount of pollen exposure (pollen counts x days) has increased, or rather just shifted to earlier dates. Another aspect of the climate change and aeroallergen story is the potential impacts of rising CO2 concentrations on plant physiology and pollen production. For example… Emberlin et al., 2002

51 Impact of Increasing CO2 Concentrations on Ragweed Allergen Production
Ragweed allergen production increases as a function of CO2 concentration For example, Singer and colleagues grew common ragweed plants under three different CO2 concentrations, 280 (pre-industrial), 370 (recent), and 600 (possible before 2100). The amount of allergenic protein produced by the plants went up substantially as a function of CO2 concentration. This is not surprising since CO2 is a plant “fertilizer.” Singer et al., 2005

52 Components of Radiative Forcing and Their Relative Impact
This slide is taken from the IPCC 4th Assessment Report. It shows the climate change potential of various atmospheric components, in terms of their radiative forcing. Positive numbers signify warming; blue cooling The size of the bar quantifies the influence of that component in the total atmosphere. Note that ozone and PM components like black carbon and sulfates (“aerosols”) play important roles here. The excess of red bars signifies that the atmosphere is getting warmer. This demonstrates that some pollutants which are of pubic health concern ALSO play important roles in climate change. IPCC, 2007b

53 Actions to Reduce Emissions from Fuel Combustion Will…
Improve public health via reductions in local and regional concentrations of PM, ozone, and other toxic air pollutants Reduce human influence on global climate by reducing CO2 emissions To the extent possible, these two “environmental health” goals should be addressed in an integrated, systematic way Because climate change and air quality are so interconnected, it’s clear that we need to consider them together when thinking about ways to address one or the other. In this way, we can account for the health co-benefits and equity dimensions of climate mitigation measures aimed at reducing human influence on climate. STRATUS CONSULTING

54 Conclusions: CO2 Stabilization Will Require Significant Changes

55 Conclusions (cont.): CO2 Stabilization Could Generate Health Co-benefits
Public Health practitioners will be called upon to assess the health co- benefits of mitigation activities, including equity aspects. Recommended reading: 2007 IPCC reports: The Physical Science Basis, FAQ 1.1 page 94; FAQ 1.2. page 96; FAQ 1.3 page 98; FAQ 2.1 page 100 IPCC, 2007c

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