By MICHAEL KITCH, LACONIA DAILY SUN
LACONIA — Data collected by the air monitoring station at Wyatt Park indicate that while air quality has remained well within safety standards during the winter months, sporadic spikes in particle pollution have piqued the interest of Dr. Jeff Underhill, chief scientist at the Air Resources Division of the New Hampshire Department of Environmental Services.
Underhill explained that fine particulate pollution is a function of temperature inversions, which occur when the normal pattern of warm air below and cool air above is reversed, a phenomenon common to valleys in the winter months. Particulates, primarily from the smoke of wood-burning heating devices, instead of being carried aloft and dispersed by rising warm air, become trapped as the warm air acts as a lid.
Fine particles are generally no more than 2.5 micrometers around, which is 30 times smaller than a strand of hair. Concentrations of particles are measured in micrograms per cubic meter and the health standard of 35 is akin to one grain of salt in a liter bottle of air. Fine particulate pollution poses a risk to those with heart and respiratory disease, who may experience shortness of breath, chest pain and palpitations. Underhill said that for air quality to be considered unhealthy, the concentration of particles must be at or above 35 for a 24-hour period.
Concentrations measured at Wyatt Park have not approached this level. For instance, for 60 of the 72 hours ending at 1 p.m. on Thursday concentrations reported at Wyatt Park were seldom above 10, easily within the range of "good" air quality. However, on three occasions concentrations reached 20 and once, at 9 p.m. on Tuesday, climbed to 25, the highest level recorded so far but within the range of "moderate" air quality." Underhill said that the highest concentrations are usually reported at night, when the winds are generally calm and residents are heating their homes.
Underhill said that although the readings give no cause for immediate concern, "if the data looks interesting enough the monitoring program, which is scheduled to end in March, could be continued. He noted that this has been a relatively mild winter with higher than normal temperatures.
"In a colder winter," he said, "we could see higher concentrations."
He said that the concentrations recorded exceeded those reported in Concord and Manchester and "We're not sure why." Stressing that there was no need to issue an advisory, he said monitoring may be extended to find an explanation for the high concentrations.
The Department of Environmental Services installed the monitoring station last October. The station records both weather conditions and particle concentrations with the intention of developing a capacity to forecast the likelihood of poor air quality and issue advisories before they arise.
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