NAPLES, Italy — Heavy rains in Naples on Friday might have canceled an air quality advisory for this weekend — but don’t breathe easier just yet.

Every major city in the Naples area already is well over the maximum number of days for unacceptable amounts of air pollutants called particulate matter, which residents inhale.

Dozens of air-monitoring stations throughout five major cities in Campania measure for particulates 10 micrograms or smaller, commonly called PM10s, matter that measures about one-fifth the width of a human hair.

Italian law sets the acceptable level at 50.5 ug/mc — micrograms per cubic meter. Any city that surpasses the maximum acceptable reading on more than 35 days in a calendar year must enact anti-smog programs in an effort to bring the count back down. Naples has surpassed the acceptable level on 125 days.

"We report every day the information to the authorities, and from there, they implement anti-smog programs," said Giuseppe D’Antonio, with Agenzia Regionale Protezione Ambientale Campania, the regional equivalent to the U.S. EPA.

The agency reports data for five of the region’s more populated cities. As of Oct. 1, Avellino, west of Naples, surpassed the maximum value level on 63 days; Benevento, northeast of the city and in the mountains, on 62 days; Caserta, north of Naples, on 65 days; and Salerno, south and on the coast, on 64 days.

PM10s can cause allergylike symptoms for some people, including inflamed mucus membranes, runny noses and coughs, D’Antonio said. He asserts that people would need "to be exposed for a lifetime at very, very high levels" to suffer seriously damaging health effects.

But the pollutants pose an increased risk of mortality, brought on by cardiovascular or respiratory problems, said Helen Suh, associate professor of exposure assessment and environmental health at Harvard University’s School of Public Health.

Those at greater risk are the elderly, the young and the sick, especially those with breathing problems like asthma, she said

"PM10s are a broad class of particles, classified by size, and those are the particles that can enter people’s lungs," said Suh, who holds a doctorate in environmental health.

The "jury is still out" on how toxic PM10s might be, she said, with scientists believing it’s actually the smaller 2.5 ug/mc particles that might be more dangerous. Campania’s testing stations capture the smaller particles, but don’t differentiate between sizes.

The smaller pollutants are produced by combustion processes such as emissions from vehicles or the burning of fields and garbage, a common practice in Italy. The larger, called "coarse," include windblown dust or dust and dirt kicked up by passing cars, for example.

In Campania, the primary anti-smog effort is to limit traffic in the downtown areas, typically the greatest concentration of traffic and the biggest culprit in contributing to the elevated PM10s in summer, D’Antonio said. Home heating systems are the biggest culprits in winter.

But traffic bans alone have a limited effect — like a band-aid on an arterial gash. For example, in early September, when the city already had surpassed the acceptable PM10 level by 121 days, the city enacted a three-day driving ban in downtown for five hours per day. The day after the ban, Sept. 11, PM10 levels were higher-than-acceptable in two of the four locations from which officials managed to collect readings, according to ARPAC’s Web site. The city has eight monitoring sites. No readings were provided for four of the eight.

On Sept. 12, PM10 levels were higher-than-acceptable at four of the eight monitoring stations from which officials collected data. Levels were lower than the 50.5 ug/mc value at the remaining four.

So far this year, Naples has imposed its no-driving/anti-smog program 18 times, the first on Feb. 29, the most recent Sept. 10. Another was supposed to go into effect Sunday, but with Friday’s heavy rains the ban no longer is necessary, a smog program official said.

D’Antonio said limiting traffic is one of several long-term efforts to reduce pollutants.

Other measures include improved vehicle emission systems, improved home heating systems and a reduction in industrial output.

Tips on mitigating exposure to air pollutants:

n Avoid being outdoors on major city roadways, especially during rush-hour traffic.n Avoid smoking and being around cigarette smoke.n Use an air cleaner in your home.n Stay indoors on high-pollution days or when windy, with windows closed.n Don’t sit in rush-hour traffic with windows down.n Live away from major or busy roadways.n Live away from power plants and industrial areas.Helen Suh, Harvard University’s School of Public Health