Research finds link between air pollution, school absences in Texas
Children in Texas are more likely to miss school when certain types of air pollution increase — even when the levels are below the limit set by the federal government, a new study says.
The research also shows that absences decrease significantly when pollution decreases.
The study is unusual because it tracks the impact on a large group: 39 of the biggest school districts in Texas, including Dallas and Fort Worth. In El Paso, which has some of the state’s worst air pollution, the reduction in carbon monoxide levels resulted in a 0.8 percent decrease in the rate of absences.
"Kids are particularly sensitive to pollution, given their small size, high metabolic rates and developing systems," said Steven Rivkin, a professor at Amherst College in Massachusetts.
"Our study provides evidence that high carbon monoxide levels impose substantial costs on children and their families," Rivkin said. "The results also highlight the importance of close monitoring of pollution levels and research that isolates the effects of pollutants on health and the ability of children to perform their daily activities."
The health effects of air pollution are a major topic in Texas because the state is one of the most polluted in the country. A recent survey by Cook Children’s Medical Center in Fort Worth found that 1 in 4 children in North Texas has asthma, which can be both caused and aggravated by air pollution.
Historically, it’s been difficult to prove a direct cause between air pollution and student absences.
The rate of absences varies with the seasons, and it’s affected by a lot of other factors, from poverty to the weather. Previous studies in California and Utah have shown that absences increased as pollution rose, but they only covered a couple of months.
Rivkin and his co-authors compared years’ worth of attendance records from the Texas Schools Project, a database at the University of Texas at Dallas, to the results of pollution monitors run by the U.S. Environmental Protection Agency and the Texas Commission on Environmental Quality.
They used a series of statistical calculations to eliminate other variables and found a pattern linking carbon monoxide levels and absences at schools near the pollution monitors. The highest carbon monoxide levels were in El Paso, Houston and Laredo.
The researchers showed a direct link between student absences and days with high carbon monoxide levels, even after accounting for other variables. That was true even when the carbon monoxide level was as much as 25 percent below the level the EPA considers safe, which is 9 parts per billion.
Each day that the level exceeded the standard would equate to 12 or 13 absences per 1,000 students, and each day the level was 75 to 100 percent of the standard would equate to five to six absences per 1,000 students.
If every day of the six-week grading period were above the carbon monoxide standard, the researchers calculated, absences would rise by 9 percent. If every day were between 75 and 100 percent of the standard, the calculations showed that absences would rise by 5 percent.
The reverse turned out to be true, too. In El Paso, the carbon monoxide level exceeded the EPA standard on 16 days in 1986, and was within 75 percent of the standard on 19 days. By 2001, the number of exceedances had dropped to one day, and the number of near-exceedances had dropped to six. Had the amount of pollution not decreased, the findings suggest that the absentee rate would have been around 5.2 percent, instead of the actual 4.4 percent, that year.
Because air pollution is most likely to affect children with underlying health problems, the researchers believe that the biggest decrease in absences happened among unhealthy children.
The study, by Rivkin, Janet Currie of Matthew Neidell of Columbia University; Eric A. Hanushek of Stanford University and E. Megan Kahn of Amherst, was published in November in the Review of Economics and Statistics.
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