Here's another reason to watch what you breathe: Young women in two Canadian cities were more likely to seek emergency-room help for abdominal pain on days with bad air pollution, a researcher reported here.
Rates of emergency department visits for abdominal pain with no specific cause increased by up to 10 percent on days with high levels of carbon monoxide, nitrogen dioxide and particulate pollution, according to Dr. Gilaad Kaplan of the University of Calgary.
Nearly two-thirds of the diagnoses were women, and more than half of them were ages 15 to 24. The researchers did not find increases in abdominal pain visits by men on high-pollution days, although they noticed upticks in male visits a day or two after days of heavy pollution.
Kaplan reported his findings at the Digestive Disease Week conference here over the weekend.
His group studied 10 years of emergency-room records from all hospitals in Edmonton, Alberta, as well as records from a single urban hospital in Montreal. All told, the group found 118,000 cases of patients discharged after seeking treatment for abdominal pain with no known cause.
Kaplan said his study was prompted by earlier observations that abdominal pain without a known cause is frequently associated with depression and headaches, which in turn can be exacerbated by air pollution.
He also said a study on mice from the 1970s had shown that high levels of common air pollutants reduced proper function of the digestive system, suggesting a possible mechanism underlying abdominal pain.
Although his study showed stomach pain was associated with high levels of three common kinds of pollution, there was no link with increased levels of two other major pollutants -- sulfur dioxide and fine particulates (smaller than 2.5 microns).
Strangely, the rate of stomach pain admissions actually seemed to decrease when ozone levels were high.
At a Sunday news briefing announcing the findings, Kaplan could provide no explanation for any of the associations -- positive or negative -- since the study was not designed to determine causality.
In Abdominal Pain, Ozone May Be a Culprit
But he noted that ground-level ozone was a different kind of pollutant than others positively correlated with abdominal pain emergency visits.
Carbon monoxide, nitrogen dioxide and particulates are all direct waste products from fossil fuel burning, he said. Ozone, on the other hand, results from a complex chemical process in the atmosphere involving nitrogen oxides, volatile organic compounds, heat and sunlight over time.
Dr. Marcia Cruz-Correa, a gastroenterologist at the University of Puerto Rico, said the study confirmed many physicians' impression that most cases of non-specific abdominal pain involve women.
"If we could actually find something that's a trigger for this unexplained abdominal pain, we could maybe provide guidance," said Cruz-Correa, who moderated the news briefing.
Confirmation of the findings could help inform policy for pollution control and for public health warnings involving people with respiratory diseases, she said.