Abstract
A concrete block plant located in Bladensburg, Maryland, wants to expand to include a concrete batching plant on the same property. This expansion could further degrade air quality and impact the health of vulnerable residents. The purpose of this study is to provide information on volatile organic compounds (VOCs) levels near residential areas close to commuter traffic and industrial activity associated with the concrete plant. Air quality monitoring was conducted in the community at five sites: (1) Kingdom Missionary Baptist Church, (2) Bladensburg Waterfront Park, (3) Confluence area, (4) Bladensburg Elementary School, and (5) Hillcrest Apartment Complex by using the Atmotube, a wearable, real-time sensor that can measure total VOCs. Sampling was conducted in 30-minute periods to capture morning on-peak, afternoon off-peak, and evening on-peak periods. Traffic counts were also conducted at the sites mentioned earlier to evaluate vehicular activity. Average 30-minute values for cars ranged from 8.33 to 1295.33 cars, whereas mean truck values ranged from 0.00 to 137.67 trucks across all sites. The highest average car count of 1295.33 cars was observed at the confluence area. Mean VOCs concentrations ranged from 0.11 to 0.54 ppm across the monitoring locations. The maximum average VOCs level of 0.54 ppm was observed at Kingdom Missionary Baptist Church on Saturday. Also, the mean VOCs levels observed at the church (0.54 and 0.31 ppm) were higher compared with other locations on Saturday. Our results revealed spatial variations of VOCs levels across all locations. There were higher total VOCs levels at the church, which is the closest location to the concrete block plant.
Introduction
Residents of urban neighborhoods are exposed to industrial and traffic-related emissions of air pollutants, including volatile organic compounds (VOCs). VOCs such as benzene, formaldehyde, and toluene are an important set of air pollutants emitted from mobile and stationary sources in large amounts due to combustion, solvent and fuel evaporation, and tank leakage. 1 Sources of VOCs include car emissions, painting buildings, cooking, coal and gas-fired power plants, landfills, steel mills, and concrete plants. 2 In fact, power generation accounts for ∼37% of all anthropogenic VOC emissions. 3 Vehicles also are a major source of VOC emissions and account for 35% due to relatively heavy traffic and adverse dispersion conditions in urban areas, which could lead to an accumulation of high levels that can adversely affect air quality and human health in street canyons, especially in urban areas. 4 In Southern California, VOCs constitute 45% of on-road mobile source emissions and play a key role in urban and rural atmospheres, because they constitute 70% of hazardous air pollutants. 5 The study of VOCs is important due to their role in atmospheric ozone depletion, ground level ozone formation, toxic and carcinogenic human health effects, and enhancement of the global greenhouse effect. 6 Outdoor VOC concentrations are influenced by season, proximity to emission sources (industry, traffic, gas stations), and meteorological conditions such as temperature. 7
Chronic health effects associated with VOC exposure can be noncarcinogenic or carcinogenic. Noncarcinogenic effects include irritation, sensory effects, headache, eye irritation, skin irritation, and airway irritation; damage to the liver, kidneys, and central nervous system; asthma; and respiratory effects. 8 In contrast, the primary carcinogenic health effects associated with VOCs exposure are lung, blood, liver, kidney, and biliary tract cancers. 9 For example, one study linked exposure to VOCs with cancers of the brain, nervous system, skin, melanoma, endocrine system, and thyroid in Indiana. 10
In addition, exposure to VOCs may result in negative impacts on reproductive systems or birth defects. 11 Elevated VOC concentrations have been observed at high traffic intensity streets compared with low traffic intensity streets. 12 A study conducted in Kanawha County, West Virginia revealed that exposure to VOCs was associated with increased rates of chronic respiratory symptoms. 13
VOCs are regulated at the federal level by the US Environmental Protection Agency (EPA) in 40 CFR 59 (e.g., the National Volatile Organic Compound Emission Standards for Consumer and Commercial Products). 14 This regulation is based on the application of aerosol coatings, architectural coatings, automobile refinishing coatings, and consumer products. 15 VOCs regulations at the state level are required to be stringent and meet the Reasonably Acceptable Control Technology (RACT), which is the lowest level of emissions that can be attained while taking economic and technical considerations into account. 16 However, VOCs are not regulated by the US EPA as criteria pollutants in the clean air act. 17
People of color and low-income populations are disproportionately exposed to environmental hazards. For example, economically disadvantaged individuals are more likely to live in air pollution hot spots and could suffer increased health risks associated with ambient air pollution than the general populace. 18 They also have increased residential exposure to traffic and traffic-related air pollution (TRAP), and the percentage of individuals living in nonattainment air quality areas is significantly higher for Latinos and African Americans compared with Whites. 19 TRAP refers to air pollution from primary emissions related with motor vehicles (such as particulate matter, nitrogen dioxide, sulfur dioxide, benzene, etc.) and not to the widely dispersed secondary pollutants such as ozone. 20 Children of color in California are three or four times more likely to reside in highly trafficked areas than White children, and children in low-income communities have an increased risk to potential exposures from vehicle emissions. 21 A study on TRAP in a primarily low-income African and Latin American community in Hunts Point, New York, revealed that there were increased concentrations of elemental carbon found at intersections due to large truck traffic. 22
As an industrial corridor with a school bus depot, a trash company, a concrete block plant, other industrial facilities, and a high volume of industrial traffic, residents in Bladensburg, Maryland, are faced with environmental health disparities. Current levels of VOCs in areas with industrial traffic, including near the concrete block plant, are unknown. Recently, plant operators requested a special exception permit to construct a concrete batching plant on the property. The increase in diesel trucks in and out of the expanded facility could lead to changes in TRAP in the area, including VOC levels.
The aim of this study was to provide data on spatiotemporal variation in human exposure to VOCs due to commuter traffic, industrial traffic, and industrial activities near the concrete block plant. This information will provide community residents with baseline scientific information on human exposure to VOCs in close proximity to commuter and industrial traffic, and industrial activities associated with the concrete block plant. We investigated diurnal patterns based on time of day and rush hour traffic by conducting air quality assessments and traffic counts during morning on-peak (rush hour), afternoon off-peak, and evening on-peak (rush hour) periods.
Methods
Community background and site selection
Bladensburg, Maryland, encompasses an area of 1.01 square miles, sharing borders with Edmonston in the north, Hyattsville in the northwest, Cottage City and Colmar Manor in the southwest, and Cheverly in the southeast. The concrete block plant operates 6 days a week, excluding Sunday. We selected five monitoring locations due to their proximity to the plant (<1609 m from the facility). These include Kingdom Missionary Baptist Church (site 1, 12.19 m), Bladensburg Waterfront Park (site 2, 804.67 m), Bladensburg Elementary school (site 3, 643.74 m), Hillcrest Village Apartments (site 4, 804.67 m), and Confluence area (near King Pawn Auto Shop—site 5, 160.93 m), as shown in Figure 1.
Map showing the five monitoring locations near the concrete block plant in Bladensburg, Maryland.
Monitoring locations were selected based on community concerns about air pollution from the expansion of the current concrete plant, industrial traffic, and commuter traffic, and proximity to other emission sources such as a school bus depot, a trash company. These locations are important human receptor sites among children, adults, and the elderly (offices, residential, school, and recreational complexes). 23 Near roadway air quality monitoring was performed, because it would provide exposure information for individuals who live and work both near the concrete block plant and heavily trafficked roads. 24 Near roadway air quality monitoring is carried out to determine the impacts of transportation systems on local air quality, human health, and the environment. 25
Environmental assessment
Traffic counts and air quality monitoring were conducted by research staff who were trained in the operation, placement, and use of real-time sensors. Oversight and logistical support for the project was provided by senior members of the research team. This study was approved by the UMD Institutional Review Board (IRB) in March 2018.
Traffic counts
Traffic counts were performed to monitor commuter and industrial traffic at each monitoring site. Monitoring involved recording the number of motor vehicles that passed a designated checkpoint during a sampling period. Vehicles counted included cars, heavy duty trucks, buses, and vans. Heavy duty trucks were defined as trucks larger than pick-up trucks, including buses, whereas vans and sport utility vehicles were counted as cars. Traffic counts were performed manually in 5-minute intervals during each 30-minute sampling window. 26 Data were summed to produce an average count by day, monitoring site, and sample period.
VOC sensors
We used low-cost, easy-to-use, portable air pollution sensors to provide high-resolution data in near real-time. 27 The Atmotube is a small, wearable, portable device that measures the total VOCs, air temperature, and humidity in the real-time via Air Quality Score Android app. Readings are sent via Bluetooth low-energy protocol to a mobile phone. The device has an LED color that represents the Air Quality Score and alerts you whenever the air is unsafe. Measurements are uploaded to a secure cloud and are aggregated on the air quality map. One Atmotube sensor was worn around the neck of study staff in the breathing zone at the six monitoring locations during sampling periods.
Air quality monitoring was conducted in June 2018, Monday through Saturday when the facility was operating. Monitoring occurred during traffic peak periods (8:30 am to 9:15 am [morning] and 4:00 pm to 5:15 pm [evening]) and off-peak periods (11:00 am to 12:15 pm) in a 30-minute time frame. To capture periods with less commuter traffic, monitoring was also conducted on Saturday at the same monitoring times, compared with Monday to Friday when there was more commuter traffic.
Statistical analysis
Box plots were used to display the descriptive statistics at the five locations at different times of the day to assess the spatiotemporal variation in VOCs. The data collected were analyzed by using SAS Enterprise Version for Windows 9.3. Data obtained from traffic counts were categorized into weekdays (Wednesday and Thursday) and weekends (Saturdays). Traffic counts recorded were expressed as the mean counts of cars and trucks observed on the monitoring days.
Results
Demographic analysis
Table 1 provides population statistics for Bladensburg. There are 9,148 residents, with 53.1% female and 46.9% male. 28 According to the 2010 census, 65.6% of the residents were African American whereas Hispanics were 26.9% of the population. 29 In Maryland, 29.4% are African American whereas 8.2% of the population are Hispanics. Also, 73.2% of the population were 18 years and older, with nearly 29% of the population aged 18–24 years with less than high school education. In Bladensburg, the median household income was $34,966 and 14.6% of community residents lived in poverty compared with 9.7% in Maryland.
Sociodemographic Composition of Bladensburg
Box plots for total VOCs
Descriptive statistics were calculated for total VOC levels at the five locations on six monitoring days. The box plots that display the distribution of observed data are shown in Figures 2–4.
Boxplots of VOCs at the five locations obtained during the morning shift on the 6 days on which monitoring occurred. [
Box plots of VOCs at the five locations obtained during the afternoon shift on the 6 days on which monitoring occurred. [
Box plots of VOCs at the five locations obtained during the evening shift on the 6 days on which monitoring occurred. [
Figure 2 provides the box plots of VOCs measurements recorded in the morning during the 6 days that monitoring occurred at the five locations. Site 1 (Kingdom Missionary Baptist Church) had the highest maximum VOCs levels except on Wednesday (June 13, 2018) compared with other locations. We observed that on Thursday (June 7, 2018), sites 1, 3, and 4 had similar interquartile ranges. On Saturday (June 9, 2018), the interquartile ranges recorded at sites 1 and 2 were similar. Also, the interquartile ranges observed on Wednesday (June 13, 2018) at all sites were similar. The box plots indicate that residents may be exposed to high levels of VOCs during the morning period at Kingdom Missionary Baptist Church, likely due to the activities of the concrete block plant.
VOCs concentrations that were recorded in the afternoon on the six monitoring days at the five locations are shown in the box plots in Figure 3. The highest median, interquartile range, and maximum values were recorded at site 1 compared with other locations. The highest maximum VOCs level in the afternoon of 0.7 ppm was observed at site 1 on Thursday (June 7, 2018). Also, site 1 and site 3 on Wednesday (June 6, 2018) recorded maximum values of 0.6 ppm.
The box plots in Figure 4 are the measurements recorded in the evening at the five sites on the six monitoring days. The maximum values recorded at site 1 were higher than the other four locations on all monitoring days. The interquartile range and median values on Thursday (June 7, 2018) at site 4 were higher than those recorded at other locations. Also, on Wednesday (June 13, 2018), the maximum, median, and interquartile range values were higher at site 5 compared with other locations. We observed high median and interquartile values at site 3 on Saturday (June 16, 2018) compared with other locations. On Saturday (June 9, 2018), the median and interquartile range values were similar across all locations.
Overall, the plots reveal that the Kingdom Missionary Baptist Church had the highest maximum values of 0.9 ppm of all monitoring locations. This may indicate that residents who live, work, pray, or play close to the concrete plant are exposed to higher levels of VOCs compared with individuals who live farther away.
Analysis of traffic counts
Table 2 provides the summary of 30-minute traffic counts for cars and trucks at the five locations across different time shifts. The mean car and truck counts varied across the different sites on different days of the week. We observed that site 5 (Confluence area) had the highest value of mean car count on all monitoring days (1295.33, 1121.67, 1182.33, 748.67, 1121.67, and 1206.67). Site 3 (Bladensburg Elementary School) had the largest value of average truck count on the days that monitoring was conducted (120.33, 137.67, 122.67, 105.33, 88, and 48). The average total truck count during the weekdays had a low of 0 trucks observed at site 2 (Waterfront Park) on Wednesday (June 13, 2018). The lowest value of mean car count of 8.33 cars was recorded at site 4 (Hillcrest Apartments).
Mean of 30-Minute Traffic Counts and Total Volatile Organic Compounds in Bladensburg
VOC, volatile organic compound.
Overall, the average total VOCs levels observed at the Church (Site 1) had the highest value of 0.54 ppm (2213.11 μg/m 3 ) on Saturday (June 9, 2018), whereas a low of 0.11 ppm (450.82 μg/m 3 ) was observed at sites 3, 4, and 5 (Bladensburg Elementary School, Hillcrest Apartments and Confluence area) on Thursday (June 14, 2018). However, the highest mean total VOCS levels observed at Kingdom Missionary Baptist Church were 0.38 ppm (1557.38 μg/m 3 ), 0.21 ppm (860.66 μg/m 3 ), 0.54 ppm (2213.11 μg/m 3 ), and 0.31 ppm (1270.49 μg/m 3 ) on Wednesday (June 6, 2018), Thursday (June 14, 2018), Saturday (June 9, 2018), and Saturday (June 16, 2018), respectively. These results show that site 1 had the highest mean total VOCs concentrations on both Saturdays. Our findings show that on Saturdays, there are high levels of total VOCs concentrations near the concrete block plant. Based on the results, we observed that the Confluence Area, Bladensburg Elementary School, and Waterfront Park were near heavily trafficked roads on both weekdays and weekends, with the range of mean total VOCs levels 0.32–0.11 ppm (1311.48–450.82 μg/m 3 ). We also observed that there was a weak positive association between total VOCs and proximity to diesel truck traffic. This implies that the highest average total VOCs concentration were not always observed at locations with the highest average 30-minute truck traffic.
Discussion
The average total VOCs concentrations observed during the weekdays and weekends in Bladensburg highlight their spatial variation across the monitoring sites. The highest mean total VOCs level observed at the Kingdom Missionary Baptist Church was 0.54 ppm (2213.11 μg/m 3 ) on Saturday. The results indicate that total VOCs levels were generally higher at the church compared with other monitoring sites on Saturdays (0.54 and 0.31 ppm) (2213.11 and 1270.49 μg/m 3 ). This may be due to its proximity to the concrete block plant (< than 15 m), use of diesel vehicles (trucks) as a major source of traffic around the plant, and diesel truck trips/day in and out of the facility. Also, the mean total VOCs levels at the church (0.21–0.54 ppm) (860.66–2213.11 μg/m 3 ), Waterfront Park (0.12–0.38 ppm) (491.80–1557.38 μg/m 3 ), and Bladensburg Elementary School (0.11–0.32 ppm) (450.82–1322.48 μg/m 3 ) were higher, compared with Hillcrest Apartments (0.11–0.28 ppm) (450.82–1147.54 μg/m 3 ) and Confluence Area (0.11–0.28 ppm) (450.82–1147.54 μg/m 3 ) on all days, particularly on Saturdays.
Our findings show that the Confluence area had the highest average car counts (748.67 to 1295.33) on all monitoring days compared with other locations. We observed that the highest average truck counts were recorded at Bladensburg Elementary School (48 to 137.67) compared with other locations on the days that monitoring occurred. The results indicate that the Confluence area (site 5) and Bladensburg Elementary School (site 3) were heavily trafficked areas due to the high average car and truck counts of 748.67 to 1295.33 cars (site 5), 454 to 521.67 cars (site 3), 26 to 96 trucks (site 5), and 48 to 137.67 trucks (site 3), respectively. The highest maximum VOC value of 0.9 ppm (3688.52 μg/m 3 ) was recorded at Kingdom Missionary Baptist Church, which had low average car and truck counts (66.67–95.67 cars and 5.33–19 trucks) compared with 0.6 ppm (2459.02 μg/m 3 ) at site 3 and 0.69 ppm (2827.87 μg/m 3 ) recorded at site 5.
Our findings reveal that the recorded mean total VOCs concentrations were somewhat higher than those reported in other studies. In a study of VOCs at five municipal solid waste sites in Mexico, toluene levels at three sites ranged from 2 to 100 ppm. 30 The average benzene values observed at three municipal landfills in southern Italy were 0.5 ± 0.1, 0.6 ± 0.2, and 0.8 ± 0.3 μg/m 3 . 31 In an urban industrial setting located in Northern Spain, ambient average VOCs (BTEX) levels ranged from 2.15 to 13.26 μg/m 3 . 32 In Catalonia, Spain, average benzene concentrations (1.5 μg/m 3 ) were observed at an industrial area with petrochemical plants and oil refineries. 33 A study conducted near a landfill in Kocaeli, Turkey, recorded average concentrations of BTEX of 140.3, 1271.7, 239.9, and 341.3, respectively. 34 Total VOCs levels measured in Michigan, the United States, had mean values of 12.85 μg/m 3 across all seasons, 6.99 μg/m 3 during the summer and 11.91 μg/m 3 during the winter, respectively. 35
In Amsterdam, researchers found outdoor concentrations of 5.7 μg/m 3 in high traffic areas and 3 μg/m 3 in low traffic areas. 36 A study in Izmir, Turkey, recorded benzene and toluene levels from traffic of 11.6 ppb in air and 26.7 ppb in air, respectively. 37 A study that looked at variations in VOCs levels due to vehicular emissions at Changchun, China, recorded mean total VOC levels that ranged from 180 to 723 μg/m 3 across the five locations. 38 Another study in Hong Kong recorded mean roadside levels of benzene, toluene, and ethylbenzene as 26.7, 77.2, and 3.1 μg/m 3 . 39
Our study had some limitations. We did not utilize geographic information systems and spatial analysis to address the role of topography and weather conditions in the gradient of pollution levels in our study area. The short duration of VOCs measurements restricts our ability to make inferences about the long-term relationship between VOCs levels, traffic, and industrial activities associated with the concrete block plant. VOC levels were only recorded during the summer. We need to perform longer-term monitoring to calculate annual averages or evaluate seasonal differences in VOCs in Bladensburg. Also, land use regression models could be used to estimate individual exposure levels and account for spatial exposure gradients.
We experienced some challenges with the real-time sensors. The Atmotubes are efficient at the recommended temperature of −5°C to 50°C. 40 The performance of the sensors may be compromised when used beyond the recommended temperatures, which may have affected our data. The sensor measured total VOCs, and we were unable to determine the speciation of the VOCs found at the monitoring locations. Sorting and cleaning the downloaded data from the device was challenging, because the device was not designed to save the monitoring sessions. Rather, the device recorded VOCs levels continuously even when it was not in use and lumped all measurements together. Also, there was a lack of established quality assurance and quality control measures by the manufacturers. For instance, calibration of the device or firmware occurs when the device is connected to the app on a mobile device. Also, the Atmotube sensors have not undergone federal reference or federal equivalent methods (FEM) field testing.
Conclusion
Our study revealed spatiotemporal variations in VOCs levels in Bladensburg and may provide baseline information on residential exposure to VOCs due to commuter traffic, industrial traffic, and industrial activities associated with the concrete block plant and other local sources. The findings of our work may improve the knowledge and understanding of residential VOCs exposures within differentially burdened communities of color. Also, in future, we will conduct air quality monitoring by using stationary low-cost, and real-time sensors all year round to capture seasonal variations. We will co-locate the low-cost stationary sensors with FEM sensors to identify locations that are air pollution hot spots within the community.
Footnotes
Acknowledgments
The authors would like to acknowledge the assistance and the participation of the residents of Bladensburg, Port Towns Environmental Action (PTEA), B5 Initiative, and other local and statewide community stakeholders for their contribution. They wish to especially thank the student interns who assisted with the project.
AUTHOR DISCLOSURE STATEMENT
No competing financial interests exist.
FUNDING INFORMATION
No funding was received for this article.