# Chapter 2

Risk

- Based Strategy

2012 PM2.5 Plan SJVUAPCDSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan This page intentionally blank.San Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 1 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan 

### Chapter 2 : Risk

- B ased Strategy

2.1 WHAT IS THE RISK

- BASED STRATEGY?

The U.S. Environmental Protection Agency’s (EPA) National Ambient Air Quality Standards (NAAQS) are the primary driving force for new emissions controls that result in air quality improvements and health benefits to Valley residents

. In the conventional planning process for attaining these standards , success in protecting public health is defined by whe ther the standards are met at all air monitors. In effect, the reduction in PM2.5 mass , which shows progress toward attainment of the standard

, serves as the surrogate for population exposure and risk.

NAAQS are indeed health

- based, and attaining these standards will result in clear and significant health benefits. However, NAAQS, as currently established, are essentially

mass

- based standards . In the case of PM2.5, the current standards do not account for particle size distribution, chemical species c omposition , surface area, and o ther factors of health risk

. There is inherent complexity in documenting the health risks associated with exposure to particles (which have a wide range of characteristics) as compared to pollutants like ozone (which has mor e consistency between molecules).

In contrast, recent health

- science research has substantially deepen ed our knowledge of air pollutant health risk beyond the current Clean Air Act ( CAA ) framework and EPA standards. There is a growing recognition within the scientific community that the NAAQS alone can be incomplete measure s of public exposure to air pollution. Thus, while the CAA’s NAAQS and state implementation plan ( SIP ) process is motivated by public health, the process alone does not fully address public health impacts of ambient air pollution. To full y address potential public health benefits, an attainment strategy can use a more comprehensive, multidimensional population exposure assessment approach that goe s beyond ambient mass measurements

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EPA policy directly acknowledges the importance of a Risk

- based Strategy to maximize public health benefits within a region’s efforts to attain the National Ambient Air Quality Standards (NAAQS). EPA’s March, 2012, PM 2.5 implementation guidance memo states, “...it is likely that SIPs for the 2006 24

- hour PM2.5 NAAQS may need to include greater emphasis on reducing emissions from local sources [emphasis added] as compared to plans to attain the 1997 PM2.5 NAAQS.” 2 EPA’s m emo further encourages that states consider evidence from published literature indicating that reductions of direct PM2.5 have a greater health benefit per ton than reductions of other criteria

1 Lippman , M. (2012, April 16). Presentation: Results from National Particle Component Toxicity (NPACT) Program and NYU: Toxicology Findings, Integration, and implications. Presented at the Annual Meeting of the Health Effects Institute (HEI) in Chicago, IL, April 15

– 17, 2012. Presentation retrieved from http://www.healtheffects.org/Slides/AnnConf2012/Lippmann

- MonPM.pdf
2 U.S. Environmental Protection Agency (2012, March 2). Memorandu m from the Office of Air Quality Planning and Standards: Implementation Guidance for the 2006 24

- Hour Fine Particle (PM2.5) National Ambient Air Quality Standards (NAAQS). Retrieved from http://www.epa.gov/ttn/naaqs/pm/pdfs/20120302_implement_guidance_24

- hr_pm2.5_naaqs.pdfSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 2 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan pollutants, such as SO2 and NOx, 3 and that providing methods l ocal air quality plans can use to maximize health benefits and minimize risk inequality. 4

In September 2010, the District Governing Board adopted a research

- driven Risk

- b ased Strategy (RBS) designed to maximize public health improvements resulting from t he District’s attainment strategies and related initiatives

. The overall goal of the RBS is to minimize cumulative population exposure to air pollu tion and corresponding health risk in the region . This risk reduction goal is being pursued through the integration of emerging scientific knowledge into the District’s control strategies, incentive progra ms, public communication , and enforcement actions

. The District is integrating the RBS into the development of the 2012 PM2.5 Plan

. The purpose of this chapter is to document the scientific foundation for the RBS and how it is being applied to the District’s PM2.5 SIP

. This chapter includes the following elements:

 The key aspects of particulate pollution that shape human exposure an d risk from PM2.5 , along with a discussion of how the RBS is reflected in existing District programs ;

 Further detail s about key health risk elements of PM2.5 particles and exposure ; and

 An outline of how these risk elements are used to characterize the associated risk when evaluating sources of PM2.5 and related control or incentive options in subsequent chapters

.

2.2 BACKGROUND FOR THE R ISK

- BASED STRATEGY

As a response to mounting epidemiological evidence that PM2.5 was more harmful than PM10, EPA e stablished a PM2.5 NAAQS in 1997 to accompany the previously established PM10 NAAQS . PM10 occurs at l arger mass concentrations than PM2.5, so the shift to PM2.5 somewhat conflicted with the time

- tested toxicological precept of “the dose (mass) makes the poison.” P articulate inhalation studies found that the smaller PM2.5 particles penetrate more deeply in to the lungs

, where particles more effectively avoid immune system d efenses. T oxicological analyses of PM2.5 identified chemical species that acted differentially to promote respiratory and cardiovascular inflammation. While it was unclear at that time which PM2.5 chemicals were the most harmful, the scientific consensu s was that the health risks stemmed from the chemicals rather tha n the particles themselves.

In the 15 years since the first PM2.5 NAAQS was established , scientists have conducted many studies that have i dentified which chemical species of PM2.5 are most

3 Fann, N., Fulcher, C.M., & Hubbell, B.J. (2009). The Influence of Location, Source, and Emission Type in Estimates of the Human Healt h Benefits of Reducing a Ton of Air Pollution. Air Quality, Atmosphere & Health

, 2(3) , 169

– 176. doi: 10.1007/s11869

- 009

- 0044

- 0 4 Fann, N., Roman, H.A., Fulcher, C.M., Gentile, M.A., Hubbell, B.J., Wesson, K., & Levy, J.I. (2011). Maximizing Health Benefits and Minimizing Inequality: Incorporating Local

- Scale Data in the Design and Evaluation of Air Quality Policies. Risk Analysis, 31(6) , 908

– 922. doi: 10.1111/j.1539

- 6924.2011.01629.xSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 3 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan harmful and have pinpointed their sources

. 5 H ealth researchers have also documented the negative cardiovascular and immune system effects of ultrafine particles, or particles that are 0.1 microns or smaller ( PM 0.1 ) , b ased on these particles’ ability to penetrate the alveolar region of the lungs and deliver chemicals into the bloodstream. This smaller

- is

- more

- dangerous phenomenon parallels the previous discovery regarding the higher toxicity of PM2.5 particles compared to larger and heavie r PM 10 particles. In each case, the dose

- makes

- the

- poison assumption governing the NAAQS for carbon monoxide, lead, ozone, and the ot her criteria pollutants does not apply to particulates.

A ddressing the complexity of health risks posed by particulate pollu tion has been a motivating factor in the development and application of the RBS. Rather than ignor e this growing body of scientific knowledge in the development of this SIP, the District’s RBS seeks to embrace it to the extent possible within the current CAA to maximiz e public health benefits

. In practice , this knowledge provides the District with the necessary scientific foundation for justif ying and prioritizing the pollution control

measure s that are necessary for demonstrating attainment in this plan. The outcome is

a stronger, more health

- protective plan that reflects the current trajectory of scientific knowle dge toward a more complete understanding of population risk from PM2.5 particles

.
The NAAQS

- SIP process and the RBS are complimentary strate gies, not an either

- or scenario. T he RBS should not be interpreted as a zero

- sum tradeoff that emphasizes controls on certain forms and sources of high

- risk PM2.5 while ignoring others. T he current mass

- based indicator (micrograms per cubic meter of air) will continue to serve as the final yardstick for PM2.5 attainment and as a surrogate for achieving significant health benefits

. As required under the CAA, the District is committed to attaining the 2006 PM2.5 standard as expeditiously as possible, and t he District will not ignore sources of PM2.5 under its jurisdiction that could contribute to the Valley’s attainment of the PM2.5 NAAQS

. A number of the District’s programs have been influenced by the underlying principles and goals of the Risk

- based Strategy and provide a model of the success and added potential benefits possible under this strategy.

 District Rule 4901 (Wood Burning Fireplaces and Wood Burning Heaters) and the District’s corresponding Check

- Before

- You

- Burn program have both been reduc ing harmful speci es of PM2.5 where and when those reductions are most needed

— in impacted urbanized areas when the local weather is forecast to hamper PM dispersion. By decreasing emissions from residential wood burning, Rule 4901 decreases directly emitted PM2.5

, as well as carbon monoxide, formaldehyde, sulfur dioxide, irritant gases, and known and suspected carcinogens, such as polycyclic aromatic hydrocarbons (PAH). In 2008, the Central Valley Health Policy Institute found that District wood burn ing curtailments on days with high PM concentrations reduced annual PM exposure

5 U.S. Environmental Protection Agency [EPA]. (2009). Integrated Science A ssessment for Particulate Matter: Final Report. Washington, D.C.: EPA/600/R

- 08/139F. Available at http://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=216546San Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 4 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan by about 13% in Bakersfield a nd Fresno, resulting in an estimated 59 to 121 avoided cases of annual premature mortality

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Even though t he 2008 PM2.5 Plan was developed per EP A requirements for the 1997 PM2.5 standard (with a 24

- hour standard of 65 μg/m3), the 2008 plan included a commitment to amend Rule 4901 in 2009 (with implementation in 2010) to align the wood

- burning curtailment threshold with the ne wer 2006 PM2.5 standar d (with a 24

- hour standard of 35 μg/m3). Then, based on research reiterating the effectiveness of R ule 4901 in protecting public health

, as well as public support for a stronger rule, the District amended and implemented Rule 4901 in 2008

— one year ahead o f the scheduled rule development and two years ahead of scheduled implementation. The amended rule also set the curtailment level lower than initially planned ( to 30 μg/m3 ) to provide an extra margin of safety and to address air quality forecast uncertain ties.

The significant increase in the number of curtailment days resulting from the lower threshold has resulted in a parallel reduction in nighttime neighborhood exposure to PM 0.1, including exposure that has been shown to occur as a resul t of indoor infiltration. This aspect of Rule 4901, i.e. reducing the frequency of elevated exposure to PM0.1 that induce s immune system sensitization and cardiovascular inflammation , has been carried forward into the Risk

- based Strategy

. The District’s prioritizati on of Rule 4901 is one of the best e xamples of a District policy aimed at maximizing public health benefits based on a rigorous assessment of population exposure and risk

.

 District grant programs reach beyond the current CAA NAAQS

- SIP process to reduce emissions in advance of or beyond regulations. For example, through the District’s popular Clean

- Green

- Yard

- Machine grant program, the District has replaced over 2,000 high

- polluting gas

- powered law n mowers with clean electric
mowers, thus decreasing the urban, localized health risks associated with the use of gas

- powered equipment. As described in Appendix C of this plan, the District is now expanding its lawn care emissions reductions programs to the commercial sector. In conjunction, District

- funded field measurements of PM 0.1 by UCSF

- Fresno found very high concentrations in and around lawn care activities, indicating a very high intake fraction for lawn care workers and concomitant cardiovascul ar risk.

 The District’s information and educational programs, such as the Real

Time Air Quality Advisory Network (RAAN), also contribute to the Risk

- based Strategy. RAAN uses real

- time data from air monitoring stations throughout the Valley to provide ho ur

- by

- hour air quality updates to schools and other subscribers. Subscribers can use this information to make informed decisions and plan outdoor activities for times with the best air quality, reducing potential

6 Lighthall, D., Nunes, D., & Tyner, T.R. (2009)

. Environmental Health Evaluation of Rule 4901: Domestic Wood Burning. Fresno, CA: Central Valley Health Policy Institute for the San Joaquin Valley Air Pollution Control District. Retrieved from http://www.fresnostate.edu/chhs/cvhpi/documents/wood

- burning

- report.pdfSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 5 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan air quality health risks. Reflecting the latest science on PM2.5 exposure risk for sensitive individuals, a mbi ent concentrations of PM2.5 that are used to trigger RAAN health risk warnings are more health protective than those used in the EPA’s Air Q uality Index.

 The District tracks and sponsors health research. The District has sponsored several Valley

- based health research projects in recent years. In 2010

– 2011, the District sponsored a first

- of

- its

- kind epidemiological investigation of health effects of air pollution in Modesto, Fres no, and Bakersfield. 7 The study found that high PM and ozone concentrations clearly correlate to increased hospital and ER admission rates, especially for those 19 and younger. During 2011 and 2012, the District is sponsoring a follow

- up epidemiological study to examine which of the chemicals found in Valley PM2.5 are most highly correlated with elevated ER and hospital admission rates. The District is also sponsoring a pilot study of PM 0.1 in Fresno, partnering with UCSF

- Fresno

, to investigate the quan tity and spatial distribution of PM 0.1 plumes from motor vehicles, lawn care equipment, wood burning, and restaurants. The District will continue to seek out and fund research opportunities that further the understanding of PM2.5 and ozone impacts on publ ic health.

2.3 HOW IS THE RISK

- BASED STRA TEGY BEING INCORPORA TED INTO THIS PLAN?

Though there are several existing District programs that readily fit into this strategy, this 2012 PM2.5 Plan is the District’s first formal effort to synthesize research, population

exposure analysis, and comprehensive emissions reduction s efforts into a cohesive Risk

- based Strategy . This is also the District’s first opportunity to demonst rate how the RBS fits within and effectively supplements EPA’s current CAA framework.

The District is integrating the RBS into various aspects of the 2012 PM2.5 Plan

. The District expects to incorporate the RBS into this plan with the following :

 Information regarding health effects of PM2.5 : Chapter s 1 and 2 include detailed discussions regarding the different types of PM2.5 and their associated health effects.

 Ambient data analysis: In addition to evaluating PM2.5 mass trends per CAA and EPA guidelines, Chapter 3 and Appendix A discuss PM2.5 species

- based trends. T his species analysis , when considered with health research

, will highlight which PM2.5 and PM2.5 precursor sources might be priorit ized under the RBS . The District is also evaluating the timing of higher PM2.5

7 Capitman, J. A.

, & Tyner , T.R. (2011)

. The Impacts of Short

- Term Changes in Air Quality on Emergency Room and Hospital Use in California's San Joaquin Valley

. Fresno, CA: Central Valley Health Policy Institute for the San Joaquin Valley Air Pollution Control District. Retrieved from http://www.fresnost ate.edu/chhs/cvhpi/publications/index.htmlSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 6 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan concentrations to see if there are certain times of the day or times of the year when PM2.5 reductions might have more public health benefits.

 Health Research: The RBS is driven by strong science and research, and the District will continue to evaluate existing research and assist in promoting new research relevant to the Valley.

 Analysis of health benefits under the attainment strategy: Building on regional SIP modeling provided by ARB, the District us ed EPA’s BenMAP benefit estimation model to estimate the health benefits in the Valley resulting from the District’s attainment strategy. (See section 2.5 and A ppendix E for additional details)

 Source

- by

- source assessment : The District is conducting a tho rough analysis of all potential opportunities to reduce emissions of directly emitted PM2.5 and significant PM2.5 precursors in the Valley. The qualitative exposure assessment described below will be used to assist in evaluating the potential health benefit of reducing emissions from these various sources. This more comprehensive assessment will help establish the strongest scientific justification for new source control strategies and incentive program investments.

 Control measure

/strategy prioriti zation : Based on the above source

- by

- source assessment

, and other evaluation being conducted as part of developing this plan, priority will be given to regulatory control measures, incentive programs

, technology advancement efforts, policy initiatives, and other strategies that maximize public health

.

2.4 FIVE

- FACTOR E XPOSURE ASSESSMENT METHODOLOGY

To qualitatively evaluate the potential risk reduction benefits from various sources, this plan will employ a scientifically based exposure characterization methodology that draws on the latest scientific understanding about health risk from PM2.5 exposure.

The District will use a f ive

- factor exposure assessment methodology under the RBS:

1. Relevance to attainment 2. Toxicity of chemical species 3. Particle size and deposition 4. Proximity to PM 0.1 5. Population intake fraction

The qualitative exposure assessment employed in this SIP is different than a formal risk

assessme nt. R isk assessment requires the quantification of key elements re lating to emission levels , particle or chemical toxicity, dose

- response relationships, and total population exposure. The primary drawback for formal risk assessment model s in a SIP context is pervasive empi rical un certainty regarding the values of the different el ementsSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 7 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan listed above

. Even if the chemical composition, geographic pattern and volume, and spatial distribution of emissions from a given source are known, it is very difficult to isolate and quantify the regional health impacts of emissions from that sour ce because many other sources are also contributing to PM2.5 exposure. In addition, PM2.5 aerosols undergo photochemical aging over time and space, often resulting in new secondary organic and inorganic species generated by variable regional source loads and meteorological conditions. Despite these limitations

, it is possible to use a simple but robust exposure characterization tool for making important qualitative and categorical distinctions regarding the relative contribution and associated of a given

so urce to population exposure.

2.4.1 Relevance to A

ttainment

An important element of the RBS is the relevance of the emissions reductions to the Valley’s attainment of EPA’s health

- based standards. This portion of the analysis will consider emissions type (such as PM2.5, NOx, or SOx) , seasonality of the emissions (since PM2.5 exceedance days occur during the winter months ) , and the percent contribution of that source’s emissions relative to the Valley’s total emissions inventory. For exampl e, NOx is the limiting factor for ammonium nitrate and therefore reductions of NOx emissions in the Valley will provide a greater impact to achieving attainment than

re ductions of ammonia emissions.

2. 4 .2 Toxicity of Chemical S pecies

PM2.5 particles va ry in their toxicity depending on their chemical composition. PM 2.5 particles are characterized by a widely diverse combination of chemicals depending on unique regional combinations of meteorology, topography, and pollution sources. In addition to exper imental and clinical research that has identified these toxicity differences, epidemiological studies have found regional differences in health impacts despite comparable regional PM2.5 mass exposure

. 8 B eyond the intrinsic toxicity of individual chemicals, the unique combinations of chemicals generated by some sources can actually magnify health risk above and beyond what their mass concentrations would suggest

. 9

Many emissions source s evaluated in this plan are sources of direct (primary) PM2.5 emissions characterized by a unique combination of chemi cal species

. Other sources emit chemical species such as ammonia and nitrogen oxides (NOx) , precursors that contribute to the formation of secondary PM2.5 species. The PM2.5 chemical species categories adopted in the exp osure characterization model includ e elemental carbon (carbon black), organic c arbon compounds (OC), metals (elements) , ammonium nitrate,

8 Bell, M .L . (2012)

. Assessment of the Health Impacts of Particulate Matter Characteristics . Research Report 161. Boston: MA. Healt h Effects Institute. Retrieved from http://pubs.healtheffects.org/getfile.php?u=685 9 Kelly, F .J . (2006)

. Oxidative Stress: Its Role in Air Pollution and Adverse Health Effects. Occupational Environmental Medicine

, 60

, 612

– 616 . Retrieved from http://oem.bmj.com/content/60/8/612.full doi: doi:10.1136/oem.60.8.612San Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 8 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan ammonium sulfate, and geological (see Appendix A, Se ction A.4.9). PM2.5 is regularly speciated at several Valley monitoring sites (see Chapter 3, Figure 3

- 7 ; and Appendix A). The following discussion provides an overview of PM2.5 species and their associated health impacts.

Organic carbon (OC) : OC species found in PM2.5 aerosol are ge nerated as primary organic aerosol (POA)

, predominantly through the combustion of hydrocarbons. Key POA sources include cooking, industrial processes, mobile source exhaust, prescribed burning, tire wear, and wood burning

. 10 Secondary organic aerosols (SOA) are formed from the oxidation of motor vehicle hydrocarbons, prescribed burning, wood burning, solvent use, and industrial processes.

OC is recognized as one of the most biologically reactive of PM2.5 chemical species cat egories , with ample evidence of high toxicity found in experimental, clinical , and epidemiological studies . OC, often in combination with metals such as iron, has been shown to generate reactive oxygen species (ROS) that drive several different mechani sms of pulmonary inflammation , including disruption of normal immune system functioning. 11 In addition, OC and met als have been shown to indirectly stimulate ROS production by macrophages

, which are cells responsible for defendi ng the lungs from pathogens and aerosols

. One of the primary OC species categories is polycyclic aromatic hydrocarbons (PAH). PAH species fall into two categories : a high molecular weight fraction and a low molecular weight fraction. The former is found in diesel exhaust and engine oil and is a significant risk factor for lung cancer

. 12 Low molecular weight PAH is found in other hydrocarbon combustion particles and serves as a precursor to the formation of an important OC species category known as quinones. Formed from at mospheric processing of PAH or within the body (in vivo), quinones have been shown to be one of the most important drivers of pulmonary oxidative stress, resulting in a host of negative spillover effects on immune system functioning. 13 Quinone formation vi a chemical aging of PAH occurs during multi

- day winter stagnation events in the Valley. A District

- funded clinical study of asthmatic patients in Fresno found that quinone levels in urine

10 U.S. Environmental Protection Agency [EPA]. (2004 , October )

. Air Quality Criteria for Particulate Matter : Final Report

. Washington, D.C.: EPA 600/P

- 99/002aF

- bF. Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903
11 Ayres, J. G.

, Borm, P., Cassee, F.R., Castranova, V., Donaldson, K., Ghio, A. ... Froines, J. (2008) Evaluating the Toxicity of Airborne Particulate Matter and Nanoparticles by Measuring Oxidative Stress Potential

— A Workshop Report and Consensus Statement. Inhalation Toxicology 20

, 75

– 99. Retrieved from http://faculty.unlv.edu/buckb/scanned%20pfd/Ayres%20et%20al%202008.pdf
12 Landvik, N.E., Gorria, M., Arlt, V.M., Asare, N., Solhaug, A., Lagadic

- Gossmann, D., & Holme, J.A. (2007). Effects of Nitrated

- Polycyclic Aromatic Hydrocarbons and Diesel Exhaust Particle Extracts on Cell Signalling Related to Apoptosis:Possible Implications for their mutagenic an d Carcinogenic Effects. Toxicology, 231, 159

– 174. doi:10.1016/J.tox.2006.12.009
13 Bolton, J.

, Trush, M.A., Penning, T.M., Dryhurst, G., & Monks, T.J. (2000)

. Role of Quinones in Toxicology. Chemical Research in Toxicology

, 13 (3)

, 135

– 1 60. doi: 10.1021/tx99San Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 9 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan correlated with sustained (multi

- day) high ambient concentrations o f PM2.5 and was accompanied by decreased lung function

. 14

Elemental carbon (EC) : Elemental carbon is found in combustion

- based aerosols produced by mobile exhaust (mainly diesel), wood burning, and coo king (especially charbroiling). Compared to OC species, there is limited evidence of comparable impacts on ROS production, pulmonary inflammation, and immune system disruption. For example, EC appears not to be a significant agent for the induction of inflammation in macrophage cells , i ndicating a significantly lower toxicity level relative to OC species

. 15 A recent study of PM 0.1

- based exposure of EC in mice found modest cardiovascular effects. Pulmonary inflammation was noted but only at high do s es beyond normal ambient concentration s. 16 A recent study in Mexico City found an association between exposure levels of EC and lung function decrements among asthmatic and non

- asthmatic children. 17

Characterization of health effects of elemental carbon from human exposure studies is complic ated by the high correlation between EC , OC, and metals emitted by diesel exhaust. E xposure to EC is a PM2.5 risk factor

, although there is more evidence to date that other chemical species, e.g. metals and OC, found in these particle s are the primary drivers of negative health effects

.

M etals : A combination of clinical, experimental, and epidemiological studies have implicated several of the metals found in PM2.5 with negative respiratory or cardiovascular outcomes , sometimes in conjunction with th e action of OC species . One of the most important is iron because of its ability to catalyze the production of hydrogen peroxide, leading to highly reactive hydroxyl radicals (OH) . In turn, thes e highly reactive chemicals stimulate the production and act ion of cytokines by macrophages . Cytokines

are cell

- signaling molecules that are critical to normal functioning of the immune system. A re cent experimental study examined the impact of iron in silica particle s in triggering respiratory toxicity. 18 Compared to silica particles with no iron, silica particles with iron were found to have a significantly greater effect on oxidative stress via hydrogen peroxide production with subsequent stimulus of cytokines by macrophages.

14 Ikeda, A., Vu, K.K.

- T., Lim, D., Tyner, T.R., Krishnan, V.V., & Hasson, A.L. (2012)

. An Investigation of the Use of Urinary Quinones as Environmental Biomarkers for Exposure to Ambient Particle

- Borne Pollutants. Science of the Total Environment (submitted).
15 Vogel, C. F.

, Sciullo, E., Wong, P., Kuzmicky, P., Kado, N. & Matsumura, F. (2005)

. Induction of Proinflammatory Cytokines and C

- Reactive Protein in Human Macrophage Cell Line U937 Exposed to Air Pollution Particulates. Environmental Health Perspectives 113(11)

, 1536

– 1541. 16 Vesterdal, L. K.

, Folkmann, J.K., Jacobsen, N.R., Sheykhzade , M., Wallin, H., Loft, S., & Møller , P. (2010)

. Pulmonary Exposure to Carbon Black Nanoparticles and Vascular Effects. Particle and Fibre Toxicology 7:33

. Retrieved from http://www.p articleandfibretoxicology.com/content/7/1/33 doi: 10.1186/1743

- 8977

- 7

- 33 17 Barraza

- Villarreal, A., Escamilla

- Nuñez M

. C

. , Hernández

- Cadena L

. , Texcalac

- Sangrador

. J

. L

. , Sienra

- Monge

, J

. J

. , Del Río

- Navarro

, B

., Cortez

- Lugo

, M

. , Sly

, P

. D

. , & Romieu

, I. (2011)

. Elemental Carbon Exposure and Lung Function in Schoolchildren from Mexico City. European Respiratory Journal

, 38

, 548

– 552. 18 Premasekharan, G., Nguyen, K.

, Contreras, J.

, Ramon, V.

, Leppert, V.J. & Forman, H.J. (2011)

. Iron

- Mediated Lipid Peroxidation and Lipid Raft Disruption in Low

- Dose Silica

- Induced Macrophage Cytokine Production. Free Radical Biology and Medicine

, 51(6)

, 1184

– 1194. doi: 10.1016/j.freeradbiomed.2011.06.018San Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 10 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan Extensive research relates exposure in metals (particularly nickel and vanadium) in PM2.5 to cardiovascular effects. A national epidemiological study recen tly found that communities with higher fractions of nickel, vanadium, and EC in their PM2.5 also had higher risk of cardiovasc ular and respiratory hospitalization

. 19 Specifically, cardiovascular hospitalizations were 26% higher in counties with a nickel fraction in the 75 th percentile versus counties with nickel in the 25% percentile. In an investigation of the relatively higher association between PM2.5 daily concentrations and daily rates of cardiovascular mortality in New York City, the exceptionall y high level of nickel and vanadium resulting from residual oil fly ash used for heating and as fuel for ships were identified as a principle cardiovascular risk factor

. 20 In a related study, ra ts exposed to PM2.5 with high fractions of chromium, iron, and nickel fractions responded with significantly reduced heart rate variability and increased heart rates, each being an indicator of cardiovascular disruption and risk. 21

In conclusion, metals found in PM2.5 produced from combustion of coal, residual oil, diesel fuel, and motor oil are recognized as chemical drivers of cardiovascular and respiratory morbidit y and mortality . This has led some researchers to conclude that

r egional differences in U.S. cardiov ascular mortality that cannot be explained by differences in average daily PM2.5 concent rations are likely to be caused by regional differences in coal combustion and resultant exposure to metals and OC

. 22

Ammonium nitrate: Ammonium nitrate (nitrate) is classified as a secondary inorganic species ( not directly emitted ) primary source of PM2.5

, and it does not contain carbon. Nitrate is formed by atmospheric reactions between two precurs ors : ammonia and nitric acid. Prior to this reaction, nitric acid generally originates from the chemical processing of nitrogen oxides (NOx)

, largely from fuel combustion under meteorological conditions found during Valley winters , particularly during multiday stagnation events

. As seen in Fig ure 2

- 1, nitrate is significant because it can contribute up to 50% or more to PM2.5 mass duri ng peak days during winter seasons

. The pe rc entage contribution of nitrate to PM2.5 mass is substantially reduced in summer , with the 2000

– 20 06 Valley average for Jun e ranging from 13 to 18 %, with mass levels at or below 2 μg/m 3

. 23

19 Bell, M. L., Ebisu, K., Peng, R.D., Samet, J.M. & Dominici, F. (2009)

. Hospi tal Admissions and Chemical Composition of Fine Particle Air Pollution. American Journal of Respiratory Critical Care

, 179

, 1115

– 1120. Retrieved from http://ajrccm.atsjournals.org/content/179/12/1115.full.pdf+html 20 Lippmann, M., Ito, K., Hwang, J

- S., Maciejczyk, P., & Chen, L

- C. (2006)

. Cardiovascular Effects of Nickel in Ambient Air. Environmental Health Perspectives

, 114(11)

, 1662

– 1669. Retrieved fro m http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1665439/
21 Chen, L. C.

, & Lippmann , M. (2009)

. Effects of Metals within Ambient Air Particulate Matter (PM) on Human Health

. Inhalation Toxicology

, 21 (1), 1

– 31. Retrieved from http://faculty.unlv.edu/buckb/scanned%20pfd/Chen%20and%20Lippmann%202009.pdf
22 Lippman, M. (2012, April 16). Presentation: Results from National Particle Component Toxicity (NPACT) Program and NYU: Toxicology Findings, Integration, and implications. Presented at the Annual Meeting of the Health Effects Institute (HEI) in Chicago, IL, April 15

– 17, 2012. Presentation retrieved f rom http://www.healtheffects.org/Slides/AnnConf2012/Lippmann

- MonPM.pdf 23 California Air Resources Board [CARB] . (2011) . CARB speciation data: District Staff Analysis of the 2000

- 2006 Sampler Data for the Four Speciation Samplers in the San Joaquin Valley. Available at http://www.epa.gov/ttn/airs/airsaqs/detaildata/downloadaqsdata.htmSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 11 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan Figure 2

- 1 PM2.5 Chemical Composition on Peak Days

A recent cold

- season ammonia emissions inventory for the Valley estimated that motor vehicles and livestock production each contribute approximately 40% to total seasonal ammonia. 24 Green waste composting and nitrogen fertilizer emissions from soil are also major sources. As temperatures increase, the proportional contribution of livestock to the regional inventory increases, peaking at nearly 75% of the total in the hot season

.

T he relative toxicity of ammonium nitrate is an important issue given its substantial mass contribution to regional PM2.5. The oral toxicity of nitrate is very low, with a n LD50 (dose causing death for 50% of the exposed subjects) reported to be two thirds that of table salt. This raises the question as to whether other factors intrinsic t o inhalation could lead to health effects at considerably lower exposure concentrations.

24 Battye, W., Anaja, V.P., & Roelle, P.A. (2003)

. Evaluation and Improvement of Ammonia Emissions Inventories. Atmospheric Environment

, 37

, 3873

– 3883.San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 12 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan As seen in the case of OC species, the most compelling evid ence of species toxic ity is built on a foundation of experimental, clinical, and epidemiological research . In particular, epidemiological studies draw their inferences from statistical associations between exposure variables and health outcomes only. Uncovering the actual mechanisms of harm, therefore, requires further isolation of mechanisms through experi mental and clinical research.

In the case of ammonium nitrate, evidence of toxicity is largely limited to epidemiological research alone. For example, a recent epidemiological study of traffic air toxics and pre

- term birth i n Los Angeles found statisti cal associations between nitrate mass, PAH, and several other air pollutants and the increased likelihood of pre

- term birth. 25 The authors point to other experimental studies that identified very high oxidative stress potential resulting from PAHs, metals, and other OC species collected from Los Angeles traffic sources as being the likely mechanism for pre

- term birth. They conclude by emphasizing the need to further study the links between pre

- term birth and PAH exposure.

One experimental study was foun d that explicitly looked for toxic mechanis ms driven by ammonium nitrate. 26 The study exposed rats to high concentrations of nitrate (70 to 420 μg/m 3 ) in combination with EC . After exposure, animals were sacrificed and a necropsy was performed, followed by a range of tests for pathological impacts between the control (non

- exposed) and exposed groups. The authors did not find abnormalities that could be tied to the experimen tal exposure to nitrate alone or in combination with EC

. This absence of experimental evidence for mechanisms of pathology for inhaled ammonium nitrate is consistent with its low oral toxicity.

Ammonium sulfate : Ammonium sulfate (sulfate) is also classi fied as a secondary inorganic species. It is formed when sulfuric acid, itself a product of oxidation of sulfur, reacts with ammonia. As seen in Figure 2

- 1, mass concentrations of sulfate are significantly lower than for nitrate in the Valley , averaging from 6 % to 7% of PM2.5 mass during winter peaks. Fossil fuel combustion is the primary source of sulfate in the Valley, but globally, coal combustion is the primary source. Unlike nitrate, mass concentrations of sulfate are not appreciably different in cold and hot seasons.

Research findings regarding the toxicity of sulfate are comparable to that of nitrate. Oral toxicity is low and it is approved as a food additive by the US Food and Drug Administration and the European Union

. One study 27 examined the response of 20

non

- smoking subjects to four

- hour exposure sessions in chambers containing 500 μg/m 3 of sulfate aerosol, a concentration over two orders of magnitude above ambient

25 Wilhelm, M., Ghosh, J.K., Su, J., Cockburn, M., Jerrett, M. & Ritz, B. (2011)

. Traffic

- Related Air Toxics and Pr eterm Birth: A Population

- Based Case

- Control Study in Los Angeles County, California

. Environmental Health 10: 89

. Available at http://www.ehjournal.net/content/10/1/89/ doi: 10.1186/1476

- 069X

- 10

- 89 26 Cassee, F., Arts, J.H., Fokkens, P.H., Spoor, S.M., Boere, A.J., van Bree, L., & Dormans, J.A. (2002)

. Pulmonary Effects of Ultrafine and Fine Ammonium Salts Aerosols in Healthy and Monocrotaline

- Treated Rats Following Short

Term Exposure. Inhalation To xicology , 14 (12)

, 1215

– 1229. doi: 10.1080/08958370290084872
27 Kulle, T. J.

, Sauder, L.R., Shanty, F., Kerr, H.D., Ferrell, B.P., Miller, W.R., & Milman, J.H . (1984)

. Sulfur Dioxide and Ammonium Sulfate Effects on Pulmonary Function and Bronchial Reactivity in Human Subjects. American Industrial Hygiene Association Journal

, 45(3)

, 156

– 1 61. ISSN:1542

- 8125San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 13 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan levels in the Valley. Pulmonary function tests were performed t o assess the response of these exposures. No significant changes in pulmonary function or bronc hial reactivity were observed immediately after the individual exposures or 24 hours after exposure. In an experimental study that also exposed rats to 500 μg/ m 3 of sulfate for four to eight months

, modest pulmonary impacts were noted. 28 After four months

, cellular immunologic responsiveness was not impaired, but physiologic changes were detected, including enlargement of bronchial epithelial (surfac e) cells and in alveolar size.

For each of these studies, the modest health impacts observed at very high exposure levels are consistent with the low intrinsic toxicity of sulfate. This is consistent with results of a review of the epidemiological and toxicological research on sulfate

. 29 Researchers found that PM sulfate was a weaker indicator of health risk than PM2.5

mass

. Because sulfate is correlated with PM2.5 mass , this result is inconsistent with sulfate having a strong health influence. The stu dy concluded that the epidemiologic and toxicologic evidence provide little or no support for a ca usal association of sulfate and health risk at ambient concentrations.

Geological: W int er season and annual average PM 2.5 found in the Valley contains a

ver y small fraction of species that are termed crustal , i.e. having their origins in the earth’s crust. This coarse fraction

— PM 2.5

- 10

— contains a much higher fraction , as do particles beyond the PM 10 size category. Suspended dust consist s mainly of oxides of aluminum, silicon, calcium, titanium, iron, and other metal oxides. The precise combination of these components depends on the geology

, industrial , and agricultural pr ocesses of the area. Geological material typically consists of 5 % to 15 % PM particle s

.

Other researchers examined the respiratory inflamm ation potential of PM2.5 soil dust taken from nine different sites in the western U

. S

. taken from windblown dust and vehicle

- generated particles from unpaved roads. 30 None of the sites were located in the Valley. Cultured human epithelial cells were exposed and then were assessed for their release of cytokines known to be tri ggered by oxidative stress. PM 2.5 from five of the sites was found to be benign, three of the sites demonstrate d measu rable cytokine response, and PM 2.5 from one site was found to be highly reactive. Endotoxin, a potentially reactive bio

- aerosol that is often found in PM, was not found to be a contributing factor to the variations in inflammatory potential.

Alt hough not technically a geologic species, respirable road dust ( RRD ) has been recognized and an alyzed as a separate form of PM 2.5 that has relevance to exposure

28 Smith, L. G.

, Busch

, R

. H

. , Buschbom

, R

. L

. , Cannon

, W

. C

. , Loscutoff

, S

. M

. , & Morris

, J

. E. (1989)

. Effects of Sulfur Dioxide or Ammonium Sulfate Exposure, Alone or Combined, for 4 or 8 Months on Normal and Elastase

- Impaired Rats. Environmental Research 49(1) , 60

- 78. doi: 10.1016/S0013

- 9351(89)80022

- 2 29 Reiss, R., Anderson

, E

. L

. , Cross

, C

. E

. , Hidy

, G

. , H oel

, D

. , McClellan

, R

. , Moolgavkar

, S . (2007)

. Evidence of Health Impacts of Sulfate

- and Nitrate

- Containing Particles in Ambient Air. Inhalation Toxicology

, 19(5)

, 419

- 4 49. doi: 10.1080/08958370601174941 30 Veranth, J., Rielly, C.A., Veranth , M.M., Moss, T.A., Langelier, C.R., Lanza, D.L., & Yost, G.S. (2004)

. Inflammatory Cytokines and Cell Death in BEAS

- 2B Lung Cells Treated with Soil Dust, Lipopolysaccharide, and Surface

- Modified Particles. Toxicological Science 82(1)

, 88

– 96. Retrieved fr om http://toxsci.oxfordjournals.org/content/82/1/88.full.pdf+html doi: 10.1093/toxsci/kfh24San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 14 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan characterization of sources in this plan . In this contex t, RRD is defined a s PM less than 2.5 microns in diameter that is deposited along paved roadways as a result of roadway breakdown, tire wear, brake wear, deposition of exhaust

- related particles, and other anthropogenic sources. S peciation analysis 31 of RRD in southern California identified

over 100 organic compounds including n

- alkanes, n

- alkanoic acids, n

- alkenoic acids, n

alkanals, n

- alkanols, benzoic acids, benzaldehydes, polyalkylene glycol ethers, PAH, oxy

- PAH, steranes, hopanes, natural resins, and other compound classes. This relati vely toxic mix of OC species is coincident with a range of metals associated with motor vehicle exhaust and component wear. RRD particles are re

- suspended by passing traffic, leaf blowers, and other sources for possible inhalation by individuals in

or nea r the roadway.

To conclu de, the geologic fraction of PM 2.5 found in the Valley makes a relatively s mall contribution to overall PM 2.5 mass and, by itself, has relatively low toxicity. RRD , while not of geologic origins, has been reviewed here because o f its relevance to subsequent exposure characterization of sources in subsequent chapters.

2.4.3 Particle Size and D eposition

P article size has a significant bearing on bodily deposition

, net exposure

, and corresponding health risk , even within the PM2.5 size fraction. Key metrics for deposition assessment include the percentage of inhaled particles that remain deposited and not exhaled (known as the deposition fraction) and the location where particles are deposited within the body). 32 W ithin the PM2.5 size range, particles less than 0.1 microns ( PM 0.1 ) and greater than 10 microns are least likely to be exhaled, and thus have higher deposition fractions. 33

The relationship between particle size, zone of deposition, and deposition fr acti on are depicted in Figure 2

- 2 and is summarized as follows:

A. Nasal, pharyngeal, laryngeal: As shown in Figure 2

- 2 at the upper right, the uppermost segment of the respiratory tract is the primary zone of deposition for the smallest and largest particle s. Approximately 80% of extremely small particles of one nanometer (0.001 micron) diameter or less are retained here with a comparable deposition fraction in the 10 micron diameter

. B. Tracheobronchial: The deposition fraction in this zone peaks at near ly 40% for particles with diameters between 1 and 10 nanometers. Almost 100% of the particles above the PM 0.1 size cut are either deposited in the other two deposition zones or exhaled.

31 Rogge, W. F., Hildemann, L. M., Mazurek, M. A., Cass, G. R. and Simoneit, B. R. T. (1993). Sources of Fine Organic Aerosol

— 3. Road Dust, Tire Debris, and Organometallic Brake Lining Dust

— Roads As Sources and Sinks. Environmental Science & Technology 27(9)

, 1892

- 1904. 32 International Commission on Radiological Protection [ICRP]. (1995). H uman R espiratory T ract M odel for R adiological P rotection . ICRP Publication 66.

. Annals of the ICRP 24

, 1

– 3. 33 U.S. Environmental Protection Agency [EPA]. (2004, October). Air Quality Criteria for Particulate Matter: Final Report . Washington, D.C.: EPA 600/P

- 99/002aF

- bF. Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 15 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan C. Alveolar: Deposition in the gas exchange zone of the lungs peak s in the 10 nanometer size with a gradual dissipation of deposition beyond the PM 0.1 size.

Figure 2

- 2 Relationships Between Particle S ize D istribution and Respiratory

D eposition Z ones

Deposition of very small particles in the alveolar region of the l ungs results in the delivery of their chemicals into the bloodstream where they promote cardiovascular disruption and immune system sensitization. 34 T hese chemicals can trigger heart attacks and premature death among individual s with pre

- existing heart conditions. 35 Extremely small particles can also be absorbed into the brain via the nasal tract,

34 Delfino, R. J., Sioutas, C., & Malik, S. (2005)

. Potential Role of Ultrafine Particles in Associations between Airborne Particle Mass and Cardiovascular Health. Environmental Health Perspectives 113(8)

, 934

– 946. Retrieved from http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.7938 35 Nel A. (2005)

. Air P ollution

- R elated I llness: E ffects of P articles. Science

, 308 (5723), 804

– 8 06. doi: 10.1126/science.1108752San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 16 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan bypassing the protection provided by the blood

- brain barrier. 36 The effects of particles deposited primarily in the tracheobronchial region center on respiratory function. 37

As depicted in Figure 2

- 3 , particle deposition and associated health risk is magnified by exercise in several ways

. First, the amount of inhaled air per minute rises substantially when breathing faster and more dee ply. Second, breathing harder means that particles, especially PM 0.1, are more likely to penetrate the alveolar region of the lungs where absorption into the bloodstream occurs. A 2003 study 38 found that during moderate exercise 80% of inhaled PM 0.1 was deposited in the lungs, compared with 60% lung retention while at rest (see left panel in Fig ure 2

- 3 ). However, because the volume of air exchanged per minute increases substantially during exercise, overall PM 0.1 deposition increased by 450% (right pan el). Discussed further below, this phenomenon underscores the health risk posed to individuals who work or exercise in areas where sources of hydrocarbon combustion result in very high PM 0.1 particle concentrations.

Figure 2

- 3 Particle N umber D eposition F raction (DF) and T otal P article

D eposition of PM 0.1 at R est and E xercise

36 Oberdorster, G., Sharp

, Z

. , Atudorei

, V

. , Elder

, A

. , Gelein

, R

. , Kreyling

, W

. , & Cox

, C. (2004)

. Translocation of Inhaled Ultrafine Particles to the Brain. Inhalation Toxicology

, 16(6

- 7)

, 437

– 445. 37 U.S. Environmental Protection Agency [EPA]. (2009)

. Integrated Science Assessment for Particulate Matter: Final Report

. Washington, D.C.: EPA /600/R

- 08/139F

. Available at http://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=216546 38 Daigle, C., Chalupa

, D

. C

. , Gibb

, F

. R

. , Morrow

, P

. E

. , Oberdörster

, G

. , Utell

, M

. J

. , & Frampton

, M

. W. (2003)

. Ultrafine Particle Deposition in Humans d uring Rest and Exercise. Inhalation Toxicology

, 15 (6)

, 539

– 552. doi: 10.1080/08958370304468San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 17 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan 2.4.4 Exposure to Ultrafine P articles (PM 0.1)

Elevated exposure to freshly emitted PM 0.1 is a critical health risk factor that often does not correspond to ambien t PM 2.5 concentrations at local monitors. PM 0.1 are formed through nucleation and gas

- to

- particle reactions and grow ( or sh r ink) through a number of mechanisms including condensation, coagulation, and volatilization. 39 High concentrations of primary (dire ctly emitted) PM 0.1 are typically found near fresh sources of hydrocarbon combustion, i ncluding coal plants , charbroiled meat , diesel and gasoline vehicles, wood combustion , and lawn care equipment. These combustion particles start out very small, grow larger over time and space, and evolve chemically at the same time. Secondary PM 0.1 typically is formed via particle nucleation from gas or liquids and are characterized by larger geographic scales and more uniform population exposure.
Despite being ex tremely small, PM 0.1 has an extremely high su rface area, as seen in Figure 2

- 4 . Compared to an equal mass of particles of two microns (PM 2.0) in diameter, ultrafine particles that are 1,000 times smaller (20 nanometers or PM 0.02) nonetheless have 125 t imes the surface area. 40 In addition, PM 0.1 produced by hydrocarbon combustion typically contain a rich mixture of chemicals with potential health effects, including nickel, iron, vanadium, PAH, and others. 41 Chemical potency, very high surface area, and alveolar deposition are signal characteristics of PM 0.1 from hydrocarbon combustion that result in significant health risks from chronic exposure.

Figure 2

- 4 Electron Micrograph of an Ultrafine Particle 42

39 Solomon, P. (2012)

. An Overview of Ultrafine Particles in Ambient Air. EM: Journal of the Air & Waste Management Association, May, 18

– 26

. 40 Donaldson, K., Stone, V., Clouter, A., Renwick, L., & MacNee W. (2001)

. Ultrafine Particles. Occupational Environmental Medicine 58

, 211

– 216. Retrieved from http://oem.bmj.com/content/58/3/211.short doi: 10.1136/oem.58.3.21
41 Morawska, L., Ristovski, Z., & Jayaratne, E.R . (2008)

. Ambient Nano and Ultrafine Particles from Motor Vehicle Emissions: Characteristics, Ambient Processing and Implications on Human Exposure. Atmospheric Environment

, 42 (35)

, 8113

– 8138. doi: 10.1016/j.atmosenv.2008.07.050
42 Nel A. (2005)

. Air P ollution

- R elat ed I llness: E ffects of P articles. Science

, 308 (5723), 804

– 8 06. doi: 10.1126/science.1108752San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 18 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan Sub

- populations who live or work near source s of primary PM 0.1 from hydrocarbon combustion are particularly at risk. Health scientists have generated an o verwhelming body of epidemiological (statistical) evidence tha t individuals near freeways ( less than 300 meters ) are being harmed via chronic in halation of PM 0.1 from vehicles. 43 Similarly, a recent study of residential wood burning in Cambria , California found very high neighborhood concentrations of PM 0.1 from wood smoke e ven though concentrations of PM 2.5 at the nearby ambient monitor met the federal health standard. 44 The health risk from fresh sources of PM 0.1 has important environmental justice implications to the extent that elevated exposure to near

- source PM 0.1 is concentrated in communities that already face sources of risk related to race or socioeconomic status. 45 Chronic exposure to near

- source PM 0.1 commonly occurs in locations where local mo nitors are in attainment for PM 2.5 standards and during seasons when ambient PM 2.5 concentrations are below the annual daily standard of 15 μ m/m 3

.
2.4.5 Population P roximity and Intake F raction

Estimating total exposure and net health risk from a given source of PM 2.5 requires that population proximity and population density be considered in addition to the source’s contribution to the region al PM 2.5 emissions inventory and its toxicity. In addition to factors governing net deposition of inhaled particles reviewed above, net population exposure from the source in question is also shaped by the number of exposed individuals who inhale the emis sions and the duration of exposure in conjunction with aerosol con centration levels (see Figure 2

- 5 ). Known as the intake fraction, this measure of population exposure is defined empirically as the pollutant mass inhaled divided by the mass emitted. 46 Int ake fraction is useful in connecting emissions to health risk because the mass inhaled is a better indicator of health risk than the mass emitted or airborne concentration. Two different pollutant sources with very comparable emission rates of the same po llutant can nonetheless have significantly different intake fractions depending on the surrounding population densi ty. For example, sources of PM 2.5 located in rural areas may have an intake fraction that is 10 to 100 times smaller than a comparable sourc e located within a densely populated city.

43 Gauderman, W., Vora, H., McConnell, R., Berhane, K., Gilliland, F., Thomas, ... Peters, J. (200 7 )

. Effect of Exposure to Traffic on Lung Development from 10 to 18 Years of Age: A Cohort Study. The Lancet 369(9561 )

, 571

– 577. Retrieved from http://www.thelancet.com/journals/lancet/article/PIIS0140

- 6736(07)60037

- 3/fulltext#article_upsell
44 Thatcher, T. & Kirchstetter , T. (2011)

. Assessing Near

- Field Exposures from Distributed Residential Wood Smoke Combustion Sources . Report prepared for the C alifornia Air Resources Board

. Retrieved from http://www.arb.ca.gov/res earch/rsc/10

- 28

- 11/item2dfr07

- 308.pdf 45 London, J., Huang, G., & Zagofsky, T . (2011)

. Land of Risk, Land of Opportunity: Cumulative Environmental Vulnerabilities in California’s San Joaquin Valley

. Davis, CA: U niversity of C alifornia, Davis

, Center f or Reg ional Change. Retrieved from http://regionalchange.ucdavis.edu/publications/Report_Land_of_Risk_Land_of_Opportunity.pdf 46 Marshall, J .D.

, & Nazaroff

, W.W. (2004 , October )

. Using Intake Fraction to Guide ARB Policy Choices: The Case of Particulate Matter

. Unpublished California Air Resources Board Report.San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 19 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan Figure 2

- 5 Simplified Intake Fraction Model

The relevance of the intake fraction concept can be seen in a recent study of neighborhood variability in wood smoke concentrations in Cambria , California. 47 As described above, the winter study found very high concentrations of PM 0.1 on a neighborhood scale that were often not reflected in PM 2.5 concentrations measured by local air quality monitors. In effect, a single wood

- burning household had the effect of

e nveloping the adjacent and downwind homes with a PM 0.1 plume. Furthermore, the study also found that wood smoke PM 0.1 was infiltrating adjacent homes that were not burning, with an average indoor concentration found to be 74% as high as immediately outs ide the homes. Taking into consideration the length of PM 0.1 inhalation during sleeping hours, the relatively high concentration of PM 0.1 found in the plume, and the number affected of individuals in an urban neighborhood, the intake fraction resulting from the source of the wood smoke would be very high. Assuming that this nightly exposure occurred over the course of a season , the cumulative health risk to the neighborhood would be considerable and would almost certainly exceed the risk indicated by da ily concentrations of PM2.5 measured by ambient monitors.

47 Thatcher, T. & Kirchstetter, T. (2011). Assessing Near

- Field Exposures from Distributed Residential Wood Smoke Combustion Sources . Report prepared for the California Air Resources Board. Retrieved from http://www.arb.ca.gov/research/rsc/10

- 28

- 11/item2dfr07

- 308.pdfSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

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- 20 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan 2.5 HEALTH BENEFITS ACHI EVED THROUGH 2012 PM2.5 PLAN

Understanding the results of any strategy is critical to assessing the overall value and success of that strategy. As part of integrating the Risk

- Based Strategy into this plan

, the District has estimated the fundamental metric associated with implementation of the 2012 PM2.5 Plan

– the health benefits resulting from implementation of this strategy. As presented below and described in more det ail in Appendix E

, an EPA

- developed model called BenMAP has been employed in order to estimate the annual reductions in morbidity (disease) and mortality (premature death) attributable to improved air quality due to the 2012 PM2.5 Plan in the attainment year of 2019.

BenMAP is a sophisticated computer software model developed by the U.S. EPA that is well

- suited for estimating the health benefits from the 2012 PM2.5 Plan . Over the course of the past decade, ongoing progress in the fields of epidemiology and geographic information systems (GIS) have resulted in the development of computer models that are capable of estimating the health benefits of improved air quality with reasonable accuracy when properly applied. These models estimate the number of avoided cases of certain diseases and other health impairment categories, known as health endpoints, which result from a specified reduction in exposu re to criteria air pollutants, in this case, reduced exposure to PM2.5 concentrations

.

Th rough implementation of the comprehensive control strategy included in this plan and the resulting reductions in PM2.5 concentrations throughout the Valley, the District estimates the following health benefits using this model:

Table 2

- 1 : Health Benefits Achieved Through Implementation of the Plan

Health Impact Health Benefit (reduction in health impact) Premature Death 671 Acute Myocardial Infarction , Hospital Admissions 93 Asthma Age 0

- 19 , Hospital Admissions 131 Cardiovascular

, Hospital Admissions 175 Asthma Age 20

- 99

, Hospital Admissions 246 Asthma Age 20

- 99

, Emergency Room Visits 407 Asthma Age 0

- 19

, Emergency Room Visits 699 Acute Bronchitis 1,498 Upper Respiratory Symptoms 15,523 Lower Respiratory Symptoms 19,011 Asthma Exacerbation 114,376 Work Loss Days 125,138

In addition to quantifying reductions in disease and death based on improvements in county

- level PM2.5 concentrations, BenMAP can also be used as a tool to quantify the economic benefits associated with quantified health benefits. While assigning economicSan Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

- 21 Chapter 2 : Risk

- Based Strategy 2012 PM2.5 Plan values to health impacts is difficult given the tremendous social value s associated with these impacts, BenMAP attempts to assign values us ing an existing body of literature that connect s impacts to hard costs such as lost wages, or, in the case of premature death, a social value of $7.99 million per incidence. Using this model, the District estimates that implementation of the plan will achieve an annual Valley

- wide savings of $ 102 mill ion in health costs in 2019 , as outlined in the following table. Additionally, and more significantly, a social benefit of $5.36 billion is estimated for the 671 avoided premature deaths.

Table 2

- 2: Economic C osts A ssociated with Q uantified H ealth B enefits

Health Impact Health Benefit (reduction in health impact) Hospital Admissions, Respiratory $386,955 Asthma

, Emergency Room Visits $429,496 Acute Bronchitis $717,759 Acute Myocardial Infarction $3,081,686 Upper Respiratory Symptoms $3,677,083 Lower Respiratory Symptoms $4,502,994 Asthma

, Hospital Admissions $6,279,033 Cardiovascular

, Hospital Admissions $6,767,955 Asthma Exacerbation $10,660,442 Work Loss Days $19,539,004 Acute Respiratory Symptoms $46,109,557 Total $ 102,151,964San Joaquin Valley Unified Air Pollution Control District December 20, 2012

2

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- Based Strategy 2012 PM2.5 Plan This page intentionally blank.