|优秀||25 美国 AQI||PM2.5|
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|星期日, 5月 17|
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|星期一, 7月 13|
Dallas is among the most polluted cities in the United States for both PM2.5 and ozone air pollution. In 2019, Dallas failed to meet nationally mandated attainment levels for 24-hour PM2.5 pollution, ozone days, and annual PM2.5 pollution. As a result, nearly 1.5 million residents deemed ‘sensitive individuals’, including children, the elderly, and those with heart and lung disease, were at heightened risk for experiencing adverse health effects.
In 2019, Dallas’s annual air quality index level was rated “moderate,” posing some risk to sensitive groups. A report by the Environment Texas Research and Policy Center found that the Dallas-Fort Worth area experienced 106 days of poor air quality that exceeded “good” AQI standards.1
PM2.5 is the term for airborne particles measuring 2.5 micrometers or less. These particles include airborne dust, dirt, soot, smoke, chemicals, and metals, among others. Due to its very small size, PM2.5 can remain suspended in the air for long periods of time and penetrate the lungs into the bloodstream when inhaled, causing far-reaching health effects. Exposure to PM2.5 has been associated with cardiovascular and respiratory disease, cancer, and early death. 2
According to the World Air Quality Report, the city of Dallas ranked fourth in the state of Texas for PM2.5 pollution in 2019. Irving of Dallas county was the second most polluted city in Texas, trailing Longview by just 0.2 μg/m3.
The World Health Organization (WHO) recommends that annual PM2.5 exposure not exceed 10 μg/m3. In 2019, both Dallas and Irving failed to meet this standard, reaching annual PM2.5 averages of 12.3 μg/m3 and 13.7 μg/m3, respectively. In comparison, the city of Los Angeles, frequently regarded as one of the most polluted US cities, averaged 12.7 μg/m3,reporting cleaner air in 2019 than Irving and just slightly more polluted air than Dallas.
Observe real-time variations in particle pollution across Dallas county by exploring the Dallas air pollution map. While many cities tend to experience elevated pollution in population-dense areas, Dallas frequently experiences higher pollution levels near the city outskirts, where industry is primarily located.
Ozone is another dangerous and prevalent air pollutant in Dallas. The 2019 State of the Air report rated Dallas an “F” for ozone pollution for its number of annual days (weighted across two years) that exceeded ozone standards.3 From 2016 to 2018, 8.2 days were deemed unhealthy for ozone pollution, more than doubling the 3.2-day national standard. In the two decades since ozone standards were established, Dallas has never reached attainment.
Following live air quality data in Dallas and taking action when pollution levels exceed standards is the best way to reduce your exposure to harmful air pollution. Use Dallas’s forecast air quality data to plan ahead and avoid outdoor activities when pollution levels are expected to be high.
Overall, Dallas air pollution levels have improved over the last two decades. This improvement trend has not been a straight line, however. 2019 was particularly off-trend, experiencing both heightened levels of PM2.5 and ozone pollution.
Ozone levels have wavered year over year, though a trend line shows significant improvement in the long term. Since 2015, however, ozone levels have actually been on the rise. The number of ‘unhealthy’ ozone days have increased from a weighted average of 5.3 days from 2014 to 2016, to 6.7 days from 2015 to 2017, to 8.2 days from 2016 to 2018.
Pollution from increased vehicular emissions as a result of more cars on the road, poorly regulated industry as a result of loopholes and low penalties for breaching emission regulations, and other sources combined with the area’s relatively high temperatures and stagnant air make Dallas Fort Worth an ideal incubator for ozone.4 The US EPA, moreover, has made meeting targets more challenging by gradually lowering ozone standards. In recent years, ozone requirements have fallen from 75 ppb to 70 ppb in order to better serve at-risk communities. Many health experts are advocating for even lower thresholds in order to save more lives.5
In 2020, lockdown measures as a result of the COVID-19 pandemic are expected to have resulted in fewer cars on the road and slightly reduced industrial activity. It is yet to be seen how these changes will affect the city’s annual averages and attainment status.
Dallas’s unhealthy AQI is primarily the result of transportation and industry emissions.
Since 1997, emissions from transportation have increased by 27% per capita in the Dallas–Fort Worth area.6 Of the 10 most populous cities in the United States, only Chicago had a larger increase. This trend is largely attributable to a growing population, more cars on the road, and longer commutes. An estimated 76% of cars have just one person inside. The average commute (26.6 minutes) is a minute longer than the national average.
In order to reduce transportation emissions estimated to contribute to 74.8% of total emissions, residents should transition to more energy-efficient, low-emission vehicles. While Dallas has promoted carpooling, built more bike lanes, and upgraded the city fleet of vehicles, there is still opportunity to further promote change through the use of electric car rebates and an increased supply of electric vehicle (EV) charging stations.7
Industrial and petroleum activity is another major contributor to Dallas air pollution. A report published by the Environment Texas Research and Policy Center found that industrial facilities in North Texas were responsible for emitting 78,737 pounds of illegal, non-authorized air pollution in 2017.8This represented a 27% increase from the year before.
Five of Dallas’s top industry polluters include Owens Corning Insulating Systems plant in Waxahachie, a Garland Municipal Power plant, a Tamko Building Product facility in Dallas, a Conecsus facility in Kaufman County, and a Bridgeport Gas plant in Wise.9
While current laws carry severe penalties for over-polluters, these laws are rarely executed to their full potential. In 2018, Texas facilities only paid $2 million in penalties for illegal emissions - a small fraction of the $297 million that could have been levied.10 Closing existing loopholes and requiring industries to remain within the confines of the law present a significant opportunity in reducing Dallas air pollution.
In June 2020, Dallas experienced a significant albeit unusual pollution event when winds carried a thick cloud of dust from the Saharan Desert over the Atlantic and to the Dallas-Fort Worth area. The sandstorm produced the thickest dust in the area in at least 20 years, with air quality levels reaching the “unhealthy” rating.11 As deforestation becomes a growing problem as a result of our warming global climate, such international influences could become more prominent.
+ Article Resources
 Ridlington E. (2020). Trouble in the air: millions of Americans breathed polluted air in 2018.
 Xing Y, et al. (2016). The impact of PM2.5 on the human respiratory system. doi:
 American Lung Association. (2019). State of the air – 2019.
 Green Dallas. (2020). Air pollution.
 Song L. (2013, October 23). What's behind surging ozone pollution in Texas? Study to weigh role of fracking in health hazard.
 Lawrence M. (2019, October 17). DFW auto-emissions grow disproportionately to the population.
 Green Dallas. (2020). What is the city doing?
 Pabst E. (2020). Illegal air pollution in Texas: Air pollution from startups, shutdowns, malfunctions and maintenance at industrial facilities in Texas in 2018.
 Jimenez J. (2019, December 18). Report lists top 10 polluters in North Texas.
 Nowlin S. (2019, December 18). Illegal air pollution has increased exponentially in the San Antonio area, according to new report.
 Ray J. (2020, June 27). Saharan dust cloud causes North Texas air to be deemed ‘unhealthy’.