Air Pollution Control District Research Articles

Small contributions of dust to PM2.5 and PM10 concentrations measured downwind of Oceano Dunes

The Oceano Dunes State Vehicular Recreation Area (ODSVRA) is a large natural source of wind-driven dust emissions that primarily consist of particulate matter (PM) for which most of the mass is greater than 1 μm. The San Luis Obispo County Air Pollution Control District (SLOAPCD) has targeted ODSVRA emissions to reduce exceedances of the state standard of 50 μg m−3 for PM smaller than 10 μm (PM10) at a coastal monitoring site located 1 mile downwind of the dune area. To evaluate the potential effectiveness of this abatement strategy, five sets of measurements were collected during the windy afternoons of high-wind months (May and October) from 2019 to 2021 to quantify the organic and elemental composition of PM10 and PM smaller than 2.5 μm (PM2.5) samples. The five-campaign average afternoon PM2.5 composition relative to Beta Attenuation Monitor (BAM) concentrations included 14 ± 12% dust, 9 ± 9% sea salt, 4 ± 5% non-sea salt sulfate, and 8 ± 8% organic components, with the difference between BAM and the measured components contributing the remaining 66 ± 16% unidentified components. The high afternoon unidentified contribution was partially attributable to water, consistent with the increasing relative humidity during warm afternoons, since there was a lower unidentified contribution for overnight samples. The remaining unidentified components are consistent with prior measurements of semivolatile contributions of ammonium nitrate and organic compounds constituting >40% of PM2.5 in central California. The organic functional group signature in Fourier Transform Infrared (FTIR) spectroscopy for PM2.5 was similar to previously reported ambient marine aerosol, consistent with a natural marine source for most of the organic mass concentration. For PM10, the dust fraction was 11 ± 8% of BAM PM10 concentration and increased to 14 ± 10% of BAM PM10 concentration during days in which hourly BAM PM10 concentration exceeded 140 μg m−3. There was no statistically significant difference (p»0.05) between dust, sea salt, sulfate, or organic PM2.5 fractions between weekend and weekday concentrations, similar to prior findings for the region. These results are consistent with national and state assessments of the good air quality of the region and suggest that semivolatile components may cause differences between BAM and gravimetric mass concentrations for sampling times shorter than 24 h. In addition, the results demonstrate that the regulated dust abatement implemented at ODSVRA is misapplied and unlikely to improve downwind air quality significantly, since ODSVRA and other nearby sandy areas contribute only 14% of BAM PM10 and have not been shown to include toxic components.

Fetal and infant death associated with short-term ozone exposure

Background: Air pollution is linked to adverse pregnancy outcomes such as preterm births, but few studies evaluated its acute impact on fetal and infant mortality. We evaluated short-term impacts of warm-season ozone and cold-season fine particulate matter <2.5 microns (PM2.5) exposures on the risk of fetal death (>20 weeks) and infant mortality (live birth to one year). Methods: This time-stratified case-crossover analysis includes 1,880 singleton fetal deaths (2007-2011) and 3,229 singleton infant deaths (2007-2015) from the San Joaquin Valley (SJV), California. Daily ozone and PM2.5 were estimated by the SJV Air Pollution Control District and geospatially linked to maternal zip code at birth. Critical exposure windows of interest included the day of death (lag 0) up to 14 days before (lag 14). Conditional logistic regression models estimated the odds ratio (OR) and 95% confidence intervals (CI) for each 5 units increase in pollutant. Results: In warm season (May-October), a 5-ppb increase in ozone was associated with a 7% (95% CI: 2%-13%) increased risk of fetal death and 6% (95% CI: 2%-10%) increased risk of infant death within two weeks. The estimates were generally consistent from lag 0 to lag 14 for both mortality outcomes, with evidence of slightly stronger estimates for fetal death compared to infant death during certain lags. During lag 7, a 5-ppb increase in ozone was associated with a 9% increased risk in fetal death (95% CI: 5%-14%) and a 4% (95% CI: 1%-7%) increased risk in infant death. No associations were observed for cold-season PM2.5. Conclusions: Ozone exposure is positively associated with short-term risk of fetal and infant mortality in the warm season. Given the ubiquitous nature of air pollution, these associations merit further investigation. Meanwhile, efforts to minimize exposures among pregnant women may be warranted. Keywords: pollution, infant mortality, fetal death, stillbirth, pregnancy, mortality, ozone

Air pollution and preterm birth: A time-stratified case-crossover study in the San Joaquin Valley of California.

Air pollution is linked to preterm birth (PTB), but existing studies are primarily focused on chronic exposures, conducted in areas with moderate pollution, and/or subject to confounding. We investigated short-term associations between two pollutants [particulate matter <2.5microns (PM2.5 ) and ozone] and PTB, and estimated excess PTB cases potentially attributed to these pollutants. This time-stratified case-crossover study includes 196,970singleton pregnancies affected by PTB and early term birth from the San Joaquin Valley (SJV), California, USA (2007-2015). Daily ozone and PM2.5 concentrations were estimated by the SJV Air Pollution Control District and geospatially linked to maternal zip code. We used conditional logistic regression models to estimate the odds ratio (OR) and 95% confidence intervals (CI) for the associations between an interquartile range (IQR) increase in pollutants and very preterm (VPTB, 20-34weeks), moderate preterm (MPTB, 34-36weeks) and early term births (ETB, 37-38weeks). We adjusted all models for co-pollutants and meteorological factors. During warm seasons (May-October), an IQR increase in ozone was associated with 9-11% increased odds of VPTB from lag 0 (ORlag0 1.09, 95% CI 1.04,1.16) to lag 7 (ORlag7 1.11, 95% CI 1.04,1.16). Findings were consistent for MPTB and ETB. Ozone was potentially responsible for an excess of 3-6VPTBs, 7-9 PTBs and 24-42 ETBs per 1,000singleton deliveries. During cold seasons (November-April), increased PM2.5 exposure was associated with 5-6% increased odds of VPTB beginning at lag 3 (ORlag3 1.06, 95% CI 1.02,1.11). PM2.5 was associated with an excess of 1-3VPTBs, 0-3MPTBs and 6-18 ETBs per 1,000singleton deliveries. PM2.5 and ozone are associated with increased risk of VPTB, MPTB and ETB within one week of exposure and are potential contributors to the increasing PTB trend. More research is needed to further understand the role of air pollution on PTB risk.

Particulate matter emission factors using low-dust harvesters for almond nut-picking operations

ABSTRACT The lack of an available particulate matter (PM) PM2.5 emission factor for almond harvesting operations has become a challenge for particulate matter regulations and emissions inventory in California. Low-dust harvesters are viewed as one of the strategies to reduce PM emissions and help achieve the state’s PM2.5 attainment targets. This paper evaluates the potential emission reduction from using low-dust harvesters compared to the conventional. Orchard boundary measurements of PM concentrations were collected to back-calculate emission rates using inverse dispersion modeling. Emissions from four low-dust harvesters (Flory 850, Exact E3800, Weiss-McNair 9800 and Jack Rabbit) were compared to those from a conventional harvester (Flory 480) in two orchards, located in the Fresno County. Emissions of PM2.5, PM10 and total suspended particles were observed to be lower for all new harvesters compared to the conventional harvester. The range of reductions varies from about 40% to 77% in PM2.5 emissions based on emission factors generated. The average ratio of PM10 to PM2.5 emissions is about 12.5%. The results of these tests imply that these new low-dust harvesters are capable of reducing PM emissions without affecting product quality. Therefore, the San Joaquin Valley Air Pollution Control District should consider including the use of these new harvesters in the conservation management practices (CMP) for the reduction of PM emissions in the valley. Implications: The results of this research indicate that almond low-dust harvesters could potentially reduce PM emissions over traditional harvesters without any negative effect on product quality. Therefore, the use of these new harvesters should be considered as part of almond best management practices and updating of emissions inventory in the San Joaquin Valley.

Determination of silage face surface area on commercial California dairy farms

Analysis of exposed silage face surface area was conducted to better understand and provide feed management recommendations as well as evaluate potential compliance needs related to volatile organic compound emissions. Policy was developed by the San Joaquin Valley Air Pollution Control District (District) to restrict exposed surface area of silage piles to 199·7 m2 per farm if only one pile was exposed or 399·5 m2 per farm if more than one pile was exposed. Exposed surface area on piles of silages at 20 dairies was quantified to determine impacts of these surface area restrictions. Herd size ranged from 490 to 7,200 milking cows, and the number of exposed piles ranged from one to four per farm as maize and/or wheat silage. Surface area of piles was quantified based on pile measurements and geometric shapes. The measured value was compared to the estimated value using the District ‘online calculator’. The District calculator used inputs for base length and height with assumed constant relationships between base and top lengths. Five of 43 piles had >199·7 m2 of exposed surface area. Sixteen of 20 dairies with more than one exposed surface complied with the exposed surface area restriction. On average, the District calculator overestimated surface areas by 11·6% ± 14·8 (range −57·7 to 38·4%). Pile measurements and use of geometric shapes provide a more precise method to quantify exposed surface area. This will be of particular use for those operators who utilize the District calculator and find their exposed areas out of compliance.

E&amp;P Notes (October 2014)

Heavy Oil Venture Testing New Way To Control Flames and Emissions byStephen Rassenfoss, JPT Emerging Technology Senior Editor A major heavy oil producer in California has agreed to test a device that is designed to reduce emissions of smog-producing gases and increase the efficiency of gas burners. Aera Energy, a joint venture of Shell and ExxonMobil, said it has agreed to retrofit a steam-generating unit used to heat heavy oil by using a new approach from ClearSign Combustion, a small publicly traded Seattle-based company whose mission is finding new ways to manage flames using a range of industrial processes. Its first offering will be tested in boilers used by Aera to create steam to reduce the viscosity of extremely thick crude so it can be pumped from the Belridge oil field in Kern County, California. The company said it wants to see if the technology, which is designed to achieve ultralow emissions (5 ppm) of nitrogen oxide, or NOX, can help it meet a mandate from the San Joaquin Valley Unified Air Pollution Control District to reduce NOX, a component in smog, to 9 ppm or less. The ClearSign technology is the size of the flame. Its Duplex tile technology is designed to replace methods that create flames stretching out more than 10 ft with thousands of smaller ones no more than 6 in. tall, according to videos on its website. The new approach performs differently because “we have mixed fuel and air prior to ignition. The oxygen will diffuse more rapidly for shorter flames,” said Rick Rutkowski, chief executive officer of ClearSign. The key component is the thick tile on top of a gas mixing chamber, which channels a natural gas/oxygen mix through thousands of small passageways. Pad Sites Offer Openings for New Measurement Tools byStephen Rassenfoss, JPT Emerging Technology Senior Editor At the recent Unconventional Resources Technical Conference in Denver, a direct measurement of what is downhole was a theme of new products offered to operators who see the need for more data on what is working, what is not working, and what could be made to work better. The offerings had to strike a balance between gathering better data downhole and doing so at a price in line with the cost limits of companies grinding out profits by drilling hundreds of wells. And both are arriving at a time when multiwell pad sites are increasingly the focus of development. These clusters of wells reduce the space, time, and cost associated with completing multiple wells. One wants to consolidate more formation testing on site, and the other wants to sell data revealing how tightly spaced wells interact. While rolling out a tool for collecting cores and preserving their fluids, Don Westacott, chief adviser of global unconventional reservoirs at Halliburton, said the company is working on a new well-side testing service to guide development on pad sites that it expects to roll out early next year. A new tool from Baker Hughes will provide pressure and temperature data which, among other things, will allow decision makers to see if fractures from nearby wells or stages connect, creating communication that may or may not be a positive development. The data gathered is not new, but this is designed to do so at a lower cost. “They wanted fracture and early production monitoring, but at a lower cost,” said Thomas Scott, production line manager of well monitoring systems at Baker Hughes. Reusable Filtration Technology Under Development byTrent Jacobs, JPT Technology Writer A new type of organically modified silica glass that can remove a wide variety of oils and contaminants from produced and flowback water is showing promising results as it undergoes field trials. The material, commercially referred to as Osorb media, is sold by process technology provider ProSep, the only company licensed to supply it to oil and gas companies. The developer said that the media is unique to the world of filtration technologies because it can absorb and adsorb up to four times its dry mass and then be regenerated for reuse once the material has reached its sorption limit. The company has delivered four rental units and is building a larger system that is capable of regenerating the media in place. The first systems require that the media be changed out once it has filled up with hydrocarbons. The primary application that ProSep is developing the technology for is final stage polishing for water discharge from offshore production platforms and enhanced oil recovery (EOR) reinjection. Production companies have also expressed interest in using the technology as a pretreatment system on the front-end of reverse osmosis membranes to protect them from fouling.

Estimating Emissions Benefits of Bicycle Facilities with Stand-Alone Software Tools

To improve their capability to estimate the emissions reduction benefits of new bicycle facilities, the Association of Monterey Bay Area Governments and the Monterey Bay Unified Air Pollution Control District in California sought to develop a new software tool. The tool was required not only to deliver accurate forecasts with a small development budget but also to operate independently of other models, run on a platform that could be freely distributed without special software licenses, and provide user-friendly access to planners in multiple agencies with varying levels of technical skill. For these requirements to be satisfied, an incremental nested logit mode choice model was developed that pivoted off static exports of trip tables from the Association of Monterey Bay Area Governments’ existing four-step travel model. GPS traces collected from smartphone users in the region were analyzed to estimate a path-size logit route choice model, and the California Household Travel Survey was used to estimate a scaling coefficient on the best route utility. The model was implemented in an Adobe ActionScript graphical user interface. After the user edits the bicycle network in the user interface, new bicycle levels of service are skimmed, and new shares for each mode are calculated from their original shares in the no-build alternative and the change in the bicycle level of service. Finally, the emissions reduction is estimated on the basis of the distance and average speed of the vehicle trips replaced by bicycle travel. The result is an accurate, fast, freely distributable, user-friendly tool that is consistent with the forecasts produced by the four-step model.

Effects of Residential Wood-Burning Emissions during Winter Months in a Northern San Diego County Location

Ambient particulate matter (PM10 and PM2.5) and carbon monoxide (CO) due to domestic wood burning during the winter and summer months in the city of Escondido were investigated. The data collected from January 2000 to December 2010 from San Diego Air Pollution Control District's (SDAPCD's) collection station in Escondido were analyzed by both non-paired student's t-tests and Mann-Whitney U tests (significance of 0.05 for both tests). For all three pollutants, the significant differences in levels between the winter and summer months, the significant differences in levels during the days that were celebrated as holidays and normal days, and the significant differences in levels between weekends and weekdays were noted. Additionally, the significant differences in levels between night and daytime, early evening hours and night and during burning and smoldering fires were determined for hourly PM2.5 and CO data. For all emission types, traffic patterns did not match the levels of emissions on weekdays, weekends, evenings, or daytimes. Elemental and organic carbon species taken from PM2.5 data correlated with the original PM2.5 filter data. Results of our analysis suggest that wood burning is a source of PM10, PM2.5, and CO in the area.

Emissions from Gas-Fired Agricultural Burners

<abstract> Abstract. Because of the Federal Clean Air Act Amendments of 1990, the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) began defining Best Available Control Technology (BACT) for NOx emissions from cotton gin drying system gas-fired burners in its jurisdiction. The NOx emission levels of conventionally used, direct-fired burners were unknown, as was how direct-fired burners would compare against newer lo-NOx burners or against the proposed SJVUAPCD NOx emission standard of 60 ppm or less. Replicated laboratory studies were designed to determine the emissions and fuel efficiency of both direct-fired and lo-NOx burner designs. NOx emission levels during the test averaged from 3 ppm for one of the lo-NOx designs to 36 ppm for a direct-fired burner when tested over four firing rates. An economic analysis of the specific cost of NOx reduction achieved by substituting a lo-NOx burner for a direct-fired burner showed an annual capitalized cost of $13,945/tonne ($12,648/T) of NOx reduction. The SJVUAPCD has an upper limit of $10,670/tonne ($9700/T) of NOx reduction to qualify for definition as BACT. Using this economic criterion, lo-NOx burners do not meet the definition of BACT for cotton gins for the SJVUAPCD, and, based upon conferring with industry and environmental specialists, would not for the rest of the United States.

National Association of Home Builders v. San Joaquin Valley Air Pollution Control District: Ninth Circuit Directly Authorizes Regulation of Indirect Emissions Sources

National Association of Home Builders v. San Joaquin Valley Air Pollution Control District: Ninth Circuit Directly Authorizes Regulation of Indirect Emissions Sources

Harvesting equipment to reduce particulate matter emissions from almond harvest

Almond harvest accounts for an estimated 12 Gg of PM10 emissions in California each harvest season. Emissions from three new, “low-dust” almond harvesters (Exact Harvest Systems E4000; Flory Industries 8550; Weiss-McNair 9800 California Special) and one exhaust abatement device (Joe DiAnna, Clean Air Concept) were compared to those from a conventional harvester operating in the same orchard. Emissions of TSP and PM10 trended lower for all new harvesters and were significantly lower for most harvesters (α < 0.10). Significant reductions in PM2.5 emissions were observed from two harvesters as well. Fractionation analysis was not conducted on nut samples collected in the second year of the project, but differences observed in the composition of material that would be delivered to the huller between the Exact E4000 and conventional harvesters were functionally insignificant. The results of these tests imply that new harvest technologies are able to reduce PM10 emissions from one of the largest sources in the San Joaquin Valley (SJV) of California without affecting product quality. As such, use of these new harvesters should be considered a conservation measure that would help the SJV Air Pollution Control District (SJVAPCD) meet the requirements of their PM10 maintenance plan. Implications: The results of this research indicate that new harvesting technologies have the potential to substantially reduce PM emissions from almond harvest operations over traditional harvester designs without negatively affecting product quality. As such, use of these new harvesters could aid the SJVAPCD in maintaining its attainment status for PM10 and should be considered as candidate conservation management practices for producers.

Survey of dairy housing and manure management practices in California

In 2007, a descriptive survey was mailed to all dairies in Glenn (G) and Tulare (T) Counties to identify current and future opportunities of manure management practices on California dairies. The purpose was to provide baseline information for development of outreach curriculum and a decision support tool to quantify potential benefits of various N management options on dairy farms. Such baseline information is valuable to staff regulating dairy facilities (e.g., San Joaquin Valley Unified Air Pollution Control District and Central Valley Regional Water Quality Control Board), dairy trade association representatives, and technology vendors. Response rates for each county were similar at 29.7% (n=19; G) and 26.7% (n=88; T). Mean milking herd size averaged 570 (range 50 to 3,000) cows in G and 1,800 (range 196 to 9,286) cows in T. Survey data are reported by location due to differences between counties in herd size, housing facilities, and climate. Freestalls are common housing facilities (63.2%, G; 38.6%, T) and separated solids and corral scrapings are commonly used as bedding in freestalls (81.8% G and 79.4% T). The most common methods of manure collection were flushing and scraping (18.8%, G; 44.7%, T), only flushing (43.8%, G; 34.1%, T), or only scraping daily or less frequently than daily (37.5%, G; 20.0%, T). Most dairy farms in G (63.2%) and T (70.5%) used some method of separating solids from liquids. However, mechanical separation systems alone were used by 5.3% G and 11.4% T of dairy farms. Storage or treatment ponds were found on 95.9% of dairies. Respondents identified existing manure management practices and did not indicate any new technologies were in use or being considered for manure management. Survey results were used to describe the 2 predominant manure management pathways of manure collection, storage, treatment, and utilization. Survey results will be used to develop and disseminate targeted information on manure treatment technologies, and on-farm evaluation of implemented technologies related to anaerobic digesters, solid liquid separation, and pond additives.

An Analysis of Effects of San Diego Wildfire on Ambient Air Quality

The impact of major gaseous and particulate pollutants emitted by the wildfire of October 2003 on ambient air quality and health of San Diego residents before, during, and after the fire are analyzed using data available from the San Diego County Air Pollution Control District and California Air Resources Board. It was found that fine particulate matter (PM) levels exceeded the federal daily 24-hr average standard during the fire. There was a slight increase in some of the gaseous pollutants, such as carbon monoxide, which exceeded federal standards. Ozone (O3) precursors, such as total hydrocarbons and methane gases, experienced elevated concentration during the fire. Fortunately, the absence of sunlight because of the cloud of thick smoke that covered most of the county during the fire appears to have prevented the photochemical conversion of the precursor gases to harmful concentrations of O3. Statistical analysis of the compiled medical surveillance data has been used to establish correlations between pollutant levels in the region and the resultant health problems experienced by the county citizens. The study shows that the increased PM concentration above the federal standard resulted in a significant increase in hospital emergency room visits for asthma, respiratory problems, eye irritation, and smoke inhalation. On the basis of the findings, it is recommended that hospitals and emergency medical facilities engage in pre–event planning that would ensure a rapid response to an impact on the healthcare system as a result of a large wildfire and appropriate agencies engage in the use of all available meteorological forecasting resources, including real–time satellite imaging assets, to accurately forecast air quality and assist firefighting efforts.

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

Partnering Makes the Owens Lake Project Feasible

Partnering Makes the Owens Lake Project FeasibleThe Los Angeles Department of Water and Power (LADWP) is currently engaged in remediation of the nation's largest dust (PM10) emissions source: Owens Dry Lakebed. In July 1998, LADWP signed a memorandum of agreement (MOA) with the Great Basin Unified Air Pollution Control District (District) to implement dust control measures at the lakebed. Recognizing the challenging aspects of the Owens Lake...Author(s)M. MadisonR. ColesR. HarasickT. SchadeJ. NelsonG. HilleSourceProceedings of the Water Environment FederationSubjectSession 57 - International and Local Issues: Creative FinancingDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2002ISSN1938-6478SICI1938-6478(20020101)2002:12L.525;1-DOI10.2175/193864702784164019Volume / Issue2002 / 12Content sourceWEFTECFirst / last page(s)525 - 525Copyright2002Word count119

Classification of ozone and weather patterns associated with high ozone concentrations in the san francisco and monterey bay areas

Ozone concentrations exceeded the federal ozone standard on eight days between 1987 and 1992 at an elevation of 335 m in Pinnacles National Monument, the only site to do so in the Monterey Bay Unified Air Pollution Control District (bordering the San Francisco Bay Area to the south) from 1987 through 1989. There are no nearby sources of ozone precursors. Cluster and empirical orthogonal function (EOF) analysis were used to define the spatial patterns of daily ozone maxima associated with Pinnacles violations. Meteorological data were also categorized to determine the combination of conditions that were unique to the Pinnacles violation days. It was concluded from the analyses that the ozone violations at the Pinnacles site represent conditions within or just below the subsidence inversion that is associated with the semipermanent high-pressure system off the west coast. It appears that the ozone is preserved for a considerable period of time in the stable inversion and has traveled long distances. Neither the mechanism by which the ozone is originally trapped, nor the original sources of its precursors are clear from this analysis.

Performance Comparison of Three Samplers of Suspended Airborne Particulate Matter

The University of Arizona and the Pima County Air Pollution Control District conducted a comparison study of the following aerosol samplers: a standard high-volume sampler, a high-volume sampler fitted with a size selective inlet, and a dichotomous virtual impactor. Over sixty samples were collected with the colocated samplers during the first six months of 1981. The concentration (μg/m3) of suspended particulate matter and of sulfate was determined for all the samples, while the concentration of four lithophilic elements (Ca, Fe, Mg, and K) was determined on one third of the samples. Well-defined linear relationships for suspended particulate matter and sulfate were found to exist between each of the three sample collection methods over the concentrafion range encountered in this study. For these samples, there were significant differences in the particulate mass and large particle lithophilic element concentrations collected by each device. However, sulfate values obtained from the three samplers were in excellent agreement with each other. This suggests that the inlet collection efficiency for large particles differs significantly for these three sampling devices. Since the size selective inlet and the dichotomous virtual impactor samplers are each designed for collection of inhalable particles (particles of 15 μm aerodynamic diameter and smaller), they would have been expected to measure approximately equivalent particle mass concentrations. Thus, these differences are important to those interested in selecting a method for measuring airborne particle mass concentrations.

Community absestos exposure in Globe, Arizona

emission, two of the mills were ordered to close by the Pinal-Gila Air Pollution Control District in 1973. Before closing, however, the owner of one of the mill sites was successful in obtaining a rezoning of the property into a residential subdivision. Asbestos mill tailings were used as the primary landfill material before partial covering with topsoil. Before being shut down, this mill continued operations for several weeks as residents moved into the subdivision. The mill buildings, housing asbestos-laden equipment, remained standing in the midst of the mobile homes. The third mill, with its large pile of asbestos mill tailings, continues to operate a few hundred yards upwind from the mobile homes.

Review of Statistics of Extreme Values with Applications to Air Quality Data

In the field of air pollution control, the rare event is often of more significance than the common event. This is evidenced by the content of air quality standards which define acceptable upper limits of air pollution concentrations and acceptable frequencies with which such concentrations can be exceeded. The principles of extreme value statistics provide important tools for analyzing air quality data in an appropriately significant context. Part II of the paper presents applications of the theory to air quality data. First, application is made to decisions regarding the length of air monitoring experiments and the length of data records for dis-person analyses. The theory is then applied to the analysis of long term air pollution data collected by the South Coast Air Pollution Control District. The interrelations between extremes from monthly and annual samples are noted and are shown to be consistent with theory.

The Role of New Source Review Policy in the San Francisco Air Quality Maintenance Plan

A study of the role of New Source Review (NSR) Policy in the San Francisco Air Quality Maintenance Plan, which was prepared by the Association of Bay Area Governments, the San Francisco Bay Area Air Pollution Control District, and the Metropolitan Transportation Commission, showed that steady air quality improvement is compatible with industrial growth. The rubber and miscellaneous plastic product industries are among those which are not expected to be affected by NSR policies; however, these policies are expected to reduce employment in the chemicals and allied products industries by 10.0% and in the transportation industry by 12.3%. In the five years that NRS policy has been in place in the Bay Area, industry has expanded. No net increase in emissions from major new or modified sources can be permitted, but such industrial sources can operate provided that the appropriate emission offsets are found from other sources. Until much more experience is gained with the emission offsets concept, it is impossible to accurately assess what the real cost and benefits will be from continued NSR in the Bay Area.