Journal Article 1)
BACKGROUND AND OBJECTIVES
Boyle Heights is a neighborhood located on the eastern bank of the Los Angeles River, east of downtown Los Angeles. The extensive East Los Angeles Interchange (the busiest freeway interchange in the world) passes through Boyle Heights, allowing access to the Golden State (I- 5), Hollywood (U.S. Route 101), Pomona (SR 60), San Bernardino (I-10), Santa Ana (I-5), and Santa Monica (I-10) freeways. The area in and around Boyle Heights is also a major goods movement hub, with goods moving through warehouses and rail-yards on their way to and from the busy ports of Long Beach and Los Angeles. Boyle Heights is also bordered by heavy industrial areas such as the city of Vernon, home to facilities such as Exide Technologies (a lead- acid battery recycling facility) and rendering plants such as Baker Commodities, D&D Disposal Inc, West Coast Rendering, and Darling International. Local residents and community groups have expressed concern about increased levels of air toxics emitted from on-road and off-road vehicles (heavy duty diesel trucks and trains in particular) and industrial facilities, and the potential health consequences related to exposure to such pollutants, especially among children.
Following numerous requests from concerned residents and community leaders, AQMD began a comprehensive year-long monitoring study in April of 2009 of air toxic levels at the Resurrection Catholic School in Boyle Heights, in an area impacted by both local and regional pollution sources. This report discusses the air quality data collected at the Resurrection School and compares them to those obtained in other parts of the South Coast Air Basin during the same time period.
Sampling was conducted from 04/01/09 to 06/01/10 at a monitoring station located in the parking lot of the Resurrection Catholic School (3324 East Opal Street, Los Angeles, CA 90023), about 320 m south of the intersection between the Interstate 5 (I-5) and South Lorena Street (Figure 1). The monitors at Resurrection were located immediately above and only a few meters from East 8th Street. Thus, the measured levels may reflect this very local traffic influence that does not exist to the same extent in other areas of Los Angeles. Since many residents in Boyle Heights, including the children at Resurrection School, live, work or play in similar proximity to traffic sources, the Resurrection site can be considered representative of typical exposures in the area. Several particle and gaseous pollutants were monitored at this location including: fine and coarse particulate matter (PM2.5 and PM10, respectively), elemental carbon (EC, an indicator of diesel particulate emissions), hexavalent chromium (Cr6+), lead (Pb), volatile organic compounds (VOCs) and carbonyl compounds. Data collected at the Resurrection School site were then compared to those obtained at the Central Los Angeles and Rubidoux monitoring stations during the same time period. The Central Los Angeles and Rubidoux sites are two permanent AQMD’s network stations used to monitor air quality where air toxics are measured year-round.
The air pollutant known as particulate matter (PM) is made up of microscopic particles that can be inhaled into the lung and is known to have serious health impacts. Particulate matter is a criteria pollutant regulated by the U.S. EPA based on the size of the particles. All particles less than 10 microns (μm) in diameter are known as PM10 (or coarse particles) and particles less than 2.5 μm in diameter are known as PM2.5 (or fine particles). One micron is 1000 times smaller than a millimeter.
The study average PM10 mass concentration at the Resurrection School site (33.0 μg/m3) was similar to that in Central Los Angeles (31.3 μg/m3), and both were lower than the corresponding value measured in Rubidoux (40.7 μg/m3), probably because of increased re- suspension of dust particles at the latter location (Figure 2a). Because of the larger size of coarse particles, the coarse portion (2.5 to 10 μm) of PM10 particles is generally not transported far away from its source, except under high wind conditions. All daily average PM10 levels observed during this study were well below the U.S. EPA National Ambient Air Quality Standard (NAAQS) for this pollutant, which is 150 μg/m3 over a 24-hour period. The study average PM2.5 level at the Resurrection School site (16.3 μg/m3) was slightly higher than that observed in Central Los Angeles (14.7 μg/m3). This difference may be due to the fact that a different sampling method was used to measure PM2.5 at the Resurrection School site than at the Central Los Angeles (and Rubidoux) stations. This method is known to read slightly higher values (Figure 2b; see Appendix A for further details). However, the highest study average PM2.5 mass concentration was measured in Rubidoux (16.7 μg/m3), probably because the atmospheric levels of this air pollutant is primarily influenced by regional particles that are formed chemically in the atmosphere. However, emissions from motor vehicles, industrial facilities and other local PM contributions can also be important. The study average PM2.5 concentration at both the Resurrection School and Rubidoux stations exceeded the annual NAAQS for this pollutant set by the U.S. EPA (15 μg/m3). Also, the daily average PM2.5 levels at these two locations were higher than the corresponding 24-hr average NAAQS (35 μg/m3) on more than one occasion.
The study average concentration of EC found in fine particles (PM2.5 EC) was slightly higher at the Resurrection School site (2.04 μg/m3) than at the Central Los Angeles and Rubidoux stations (1.72 and 1.63 μg/m3, respectively) (Figure 2c). Elemental carbon is an indicator of diesel PM, considered by the State of California to be an air toxic. Although the EC levels at Resurrection School are similar to those observed in other dense urban areas of the Los Angeles Basin, they may reflect the close proximity of the Resurrection School site to mobile sources, such as the I-5, where heavy duty diesel trucks comprise about 6% of the total traffic volume.
Fine PM samples were analyzed for their chemical composition, which can provide information on the origin of the particles. The PM2.5 collected at the Resurrection Church, Central Los Angeles and Rubidoux stations had a similar chemical composition, probably because of the presence of similar emission sources at all three locations (Figure 3). There were slightly higher levels of crustal material and nitrate at Rubidoux as expected for an inland, dustier location. Higher levels of EC at Resurrection and Central Los Angeles reflect the proximity of those sites to diesel sources.
Airborne lead is measured by collecting and analyzing all particulate in the air, known as total suspended particulate (TSP). Like PM, airborne lead is regulated by the U.S. EPA with associated NAAQS. The highest study average lead concentration (16.8 ng/m3) was measured at the Resurrection School site. The corresponding average lead levels at the Central Los Angeles and Rubidoux stations during the same time period were 9.6 and 7.3 ng/m3 (Figure 4). Increased lead concentrations in the Boyle Heights area may be due to re-suspension of historically deposited dust accumulated on or near the nearby freeways. While lead has been completely removed from gasoline for over 30 years, some studies have shown higher lead levels leftover in soils next to busy roadways. Lead emissions from Exide Technologies or transport of re- suspended particles containing lead from the Exide facility might have also contributed to increase the atmospheric concentration of lead at the Resurrection School. However, this seems unlikely because the school is relatively far from the Exide plant (about 2.2 Km north-west) and the wind rarely blew from the Exide plant toward the Resurrection School site. In addition, the lead data collected at the Resurrection School site are not well correlated to those measured right next to the Exide plant during the same time period. In October 2008 the U.S. EPA strengthened the NAAQS for lead, lowering it from 1500 ng/m3 (quarterly average) to a more stringent 150 ng/m3 (rolling 3-month average). Although higher than the other sites, the lead levels at Resurrection School were still very low and none of the daily average or three-month average concentrations measured at the three monitoring sites during this study were close to or above the current NAAQS for lead.
Most of the trace elements in the particles measured at all three monitoring stations mainly originate from mechanical processes such as vehicle brake or engine wear (Fe) or from re-suspension of crustal materials (i.e. Mg, Ca, K, Fe, Si, and Al), and their concentrations were well within those reported in previous studies conducted in urban areas. Arsenic (As), Chromium (Cr) and other toxic trace elements were either not detected or were present in concentrations close to urban background levels. Sulfur (S), typically generated from combustion of sulfur-containing fuel and emitted as sulfate or SO2, was the most abundant trace element in all collected samples (Figure 5).
The study average Cr6+ level at the Resurrection School site (0.11 ng/m3) was similar to that measured in Central Los Angeles and in Rubidoux (0.10 and 0.11 ng/m3, respectively) (Figure 6). These levels are consistent with what is considered the urban background in Southern California, and thus do not indicate the presence of any local sources of hexavalent chromium.
Volatile organic compounds and carbonyls are organic gases, some of which are considered air toxics. They are emitted from a variety of sources, including motor vehicles and industrial facilities. With the exception of methylene chloride, the concentrations of the most abundant VOCs and carbonyls measured at the Resurrection School site were comparable to those observed at the other two monitoring stations in Central Los Angeles and Rubidoux (Figure 7). This is probably because gaseous emissions from motor vehicles are likely to be the predominant source of these volatile species at all three monitored locations and throughout the entire South Coast Air Basin. The slightly higher atmospheric levels of toluene, 2-butanone, m+p-xylenes and other VOCs measured at Resurrection School might be explained by the close proximity of this site to the I-5 and/or to nearby surface streets. The potential contribution of emissions from nearby industrial facilities cannot be excluded, but this pattern of VOC levels is consistent with mobile source emissions.
Overall, the concentrations of all air pollutants measured at the Resurrection School site are similar to those found in other dense urban areas of Los Angeles dominated by motor vehicle emissions. The atmospheric levels of diesel PM and VOCs were higher than those observed in Central Los Angeles and Rubidoux, likely due to the very close proximity of the Resurrection School site to the I-5 and busy surface streets.
Lead concentrations were higher at Resurrection School than in Central Los Angeles and Rubidoux, but almost nine times below (on average) the Federal Standard set by the U.S. EPA for this air toxic (0.15 μg/m3). Emissions from Exide Technologies or transport of re-suspended particles containing lead from the Exide facility cannot be ruled out. However, other historical sources such as re-suspension of dust accumulated on nearby roadways may be responsible for the slightly elevated lead levels at Resurrection School.