How Clean is Providence’s Air?

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Truck and car traffic and construction equipment along Route 10 next to a residential neighborhood

Everybody breathes, so clean air is critical to everyone’s health. Poor air quality is especially dangerous to people who are active outside, particularly outdoor workers, and to sensitive individuals, including older adults, children, and people with cardiac and respiratory conditions.

How is air quality classified?

Air quality in Providence is impacted both by regional air masses and by local sources, including vehicles and equipment; industrial operations; solvent and petroleum product storage and distribution; and fuel burning to produce heat, hot water, and energy. The US Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for six pollutants, which are referred to as criteria air pollutants. EPA uses an Air Quality Index (AQI) to communicate information about current or predicted air pollutant levels to the public. An AQI of 100 corresponds to a concentration at the level of the NAAQS for that pollutant. AQI values of 0-50 are classified as good air quality, 51-100 as moderate, 101-150 as unhealthy for sensitive groups, and 151-200 as unhealthy.

The Rhode Island Department of Environmental Management (RIDEM) operates a monitoring network that measures outdoor air levels of a wide range of pollutants, including the criteria air pollutants. Criteria pollutant levels in Rhode Island have decreased over time and the state currently is not in violation of any of the EPA’s NAAQS. However, those standards allow for exceedances of the NAAQS levels on a certain number of days each year. In Rhode Island, levels of two criteria air pollutants, ground-level ozone and fine particulate matter (PM2.5), sometimes exceed the NAAQS levels (AQI above 100), and may cause or exacerbate health effects on those days.

RIDEM posts predicted ozone and PM2.5 AQIs for the Providence area and other sections of Rhode Island on their website, along with a discussion of risks and recommendations for each AQI category. EPA’s AirNow interactive map displays current levels of those pollutants. Members of the public can also register with EPA’s EnviroFlash program to receive text or email alerts about predicted or measured air quality at locations they choose. That information is important because exposure to elevated ozone levels can cause respiratory symptoms and aggravate underlying lung diseases like asthma, emphysema, and chronic bronchitis and studies have linked PM2.5 exposures to a variety of respiratory and cardiac effects.

Ozone and Fine Particulate Matter

Ground-level ozone is formed from atmospheric reactions involving two classes of pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOC). NOx is emitted from fuel combustion in both mobile sources (on-road vehicles, construction and lawn care equipment, etc.) and stationary sources, including power plants, industry, institutions, commercial enterprises, and residences. Sources of VOC include petroleum products and solvents, combustion exhaust, and some natural processes. The reaction that produces ozone requires heat and light, so ozone levels are highest on hot, sunny days.

Ozone levels in Rhode Island are highly affected by pollutants emitted in upwind states, particularly when the wind direction is coming from an area with dense traffic and other emissions. Rhode Island’s ozone levels are often highest along the south shore of the state because that area is impacted by air masses from the New York metropolitan area that remain relatively intact as they move over the ocean. In 2023, the ozone NAAQS was exceeded on six days in Narragansett, five days in East Matunuck, and three days in East Providence; a good reason to check RIDEM’s predicted ozone levels and the current levels on EPA’s AirNow map before heading to the beach on a hot sunny day.

Fine particulate matter (PM2.5) levels are also highly affected by transport of pollutants from upwind areas, with some additional contribution from local sources. On several days in 2023, smoke from Canadian wildfires caused Rhode Island PM2.5 levels to climb into EPA’s “unhealthy for sensitive groups” AQI category, prompting warnings that people with heart or lung disease, older adults, and children should reduce prolonged or heavy exertion. EPA’s Fire and Smoke map shows real-time PM2.5 AQI levels, as well as the location of fires and smoke plumes. EPA’s Smoke-Ready Toolbox for Wildfires provides information about how to limit exposures. People who do not have access to an indoor environment with filtered air are of particular risk in those events.

Air monitoring at a special site on the roof of the Providence Community Health Center on Eddy St.

Air Toxics Monitoring

RIDEM monitors for a wide range of pollutants in addition to the criteria air pollutants, including VOCs, semi-volatile organic compounds, and metals. A suite of 60 VOCs are measured at four  sites: the Liston Campus of CCRI in Providence; Vernon Street in Pawtucket, which is adjacent to Interstate Route 95 (I-95) North; the Myron Francis School in East Providence, which is downwind of the Providence metropolitan area; and an upwind rural site at the Alton Jones Campus in West Greenwich. Some of the VOCs measured are hazardous air pollutants which, if present in sufficient concentrations, pose short or long-term health risks. Other VOCs, while not known to be toxic, are monitored because of their contribution to ozone formation.

As shown in the graph below, levels of benzene and 1,3-butadiene, which are carcinogens that are emitted by vehicles and other sources, tend to be highest at the Pawtucket site next to I-95 and lowest at the rural site. Some solvents, like dichloromethane, also known as methylene dichloride, tend to be highest at the Providence site. (Note that EPA recently banned most uses of dichloromethane.)  For some pollutants, like chloroform, concentrations are similar across the state.

The Providence CCRI site is approximately 0.4 miles from I-95. Providence neighborhoods that are closer to the highway would be more highly impacted by highway emissions. In a 2015 study funded by EPA, RIDEM evaluated the impact of I-95 traffic on air quality in nearby Providence neighborhoods.  These neighborhoods, including Washington Park and South Providence, are areas that have some of the highest poverty and childhood asthma rates in the state. Levels of benzene and 1,3-butadiene, as well as other mobile source VOCs, at the study sites near the highway were similar to those at the permanent site in Pawtucket near I-95 and higher than those measured at a Providence site approximately 0.5 miles from the highway.

Levels of two measures of particulate matter, black carbon and particle count, were elevated during morning rush hour at the study sites and were, on average, more than twice the levels measured at the site more distant from the highway. There are no NAAQS for black carbon or particle count, but those measurements showed that highway vehicles have a significant impact on nearby air quality. RIDEM also used hand-held equipment to measure particle count and black carbon levels at increasing distances from the highway under a variety of meteorological conditions. Measurable particle impacts extended at least 500 feet from the highway and appeared to be somewhat reduced by the presence of trees. Traffic on city streets, as well as stationary sources, also contributed to pollutant concentrations at some of the study sites.

The Port of Providence

Pollutant levels in ambient air are also impacted by emissions from nearby industrial, commercial, and institutional facilities. RIDEM conducted an EPA-funded air monitoring study in 2021-22 in areas around the Port of Providence.  Air emission sources in that area include diesel trucks, marine vessels, oil and gas storage and distribution, asphalt and cement processing, metals recycling, natural gas and utility service, and large heating plants. During the study period, RIDEM also inspected 43 facilities and logged 149 odor observations in the Port area.

Port Study Monitoring Site Locations

Concentrations of several VOCs in petroleum products and diesel exhaust tended to be highest at a site at the Providence Animal Shelter, which is located off Allens Avenue, in the midst of Port activities. The graphs below show average levels of two VOCs, benzene and 1,3-butadiene, measured at the study sites and at comparison sites, which are part of RIDEM’s permanent monitoring network. Average benzene levels at the Animal Shelter site at the Port were similar to those at the Vernon St. Pawtucket site adjacent to I-95, although the Animal Shelter levels varied more from day to day and were considerably higher on some days.  Average levels of 1,3-butadiene, which is a component of combustion exhaust, were considerably higher at the Animal Shelter site than at all other sites. Average benzene concentrations at the other study sites, which were in neighborhoods near the Port, were somewhat higher than those at the CCRI comparison site, but considerably lower than those seen at the Animal Shelter and Pawtucket sites. Because the samples were collected over 24-hour periods and were not immediately analyzed, it was impossible to link elevated levels detected in a particular sample with a specific source or activity.

What can be done?

Monitoring studies do not in themselves reduce exposures to air pollutants.  Recommendations in the 2015 highway study report include consideration of proximity to major roadways when making land-use decisions, including the siting of schools and other sensitive receptors, and minimizing exposures at existing facilities near busy roadways by locating play areas as far from the roadway as possible, planting trees or installing barriers, and designing air handling systems to limit infiltration of air contaminants into buildings. While those measures would provide some immediate benefits, increasing the use of electric cars, trucks, and buses in the place of diesel and gasoline powered vehicles is essential to address the disparity in exposures in areas abutting busy roadways.

Reducing pollutant levels in the Port area is complicated by the large number of sources and activities that may contribute to those levels.  As a follow-up to the 2021-22 monitoring study, RIDEM plans to purchase and operate SensitPOD continuous VOC monitors. Previous VOC samples were collected over 24-hour periods, which made it difficult to identify sources of elevated levels.  The continuous monitors will provide real-time data that can be linked to specific activities and sources. When a high VOC concentration is detected, the continuous monitors automatically collect an air sample for further analysis and trigger an investigation to identify the source of the elevated levels.  The agency also plans to purchase a FLIR infrared camera, which will allow inspectors to see emission plumes. RIDEM is continuing to investigate odors and to conduct compliance inspections in the area. Odors can be reported directly to RIDEM’s Office of Compliance & Inspection or via the Smell My City cell phone app. Deployment of electric equipment and vehicles at the Port is essential for reducing diesel exhaust emissions in that area.

How clean is the air in Providence? Rhode Island does not violate federal standards, but ozone concentrations in the state continue to be high on some hot summer days and PM2.5 levels are also sometimes elevated, especially when the state is affected by wildfire smoke. Like many other risk factors, each person’s exposure to toxic air pollutants is partly determined by their address. Especially if that address is near a major roadway, Port, or industrial facility.

Barbara Morin worked for many years in the Office of Air Resources at RIDEM and the Office of Healthy Homes and the Environment at the RI Department of Health. She currently is an Environmental Analyst at the Northeast States for Coordinated Air Use Management.