Smog — especially dangerous to children, seniors, and those with asthma — is getting worse in the Philadelphia region including South Jersey, most likely due to climate change, according to the American Lung Association.

The association's annual State of the Air report for 2018, released Wednesday, found that all counties monitored in the Philadelphia metro area saw increases in ground-level ozone, also known as smog.  The metro area includes from northern Delaware to the Jersey Shore, 10 counties in all.

"For ozone, with the sole exception of Atlantic County, N.J., all monitored counties in the Philadelphia metro area posted worse results than in last year's report," the American Lung Association said. That also includes an increase in the level of unhealthy days, the report states.

The association has provided a report card on air quality for 19 years. It looks at ozone pollution as well as particle pollution.

"When older adults or children with asthma breathe ozone-polluted air, too often they end up in the doctor's office, the hospital, or the emergency room," said Kevin Stewart, director of environmental health for the association's Mid-Atlantic chapter. "Ozone can even shorten life itself."

Ground-level ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight, according to the U.S. Environmental Protection Agency.  More sunlight, plus warmer weather, means smog is more prevalent in summer. Though this winter and spring have seen below-normal temperatures, prior years were among the warmest on record, accounting for more smog year round.

The report says the increase in smog "adds to the evidence that a changing climate is making it harder to protect human health." In fact, smog increased in most cities nationwide.  The report examined data from the years 2014, 2015, and 2016, the second warmest on record.

The Pennsylvania counties with the worst rankings were Philadelphia and Delaware.

Philadelphia long has had a smog problem.  Environmental groups are waiting to see if the EPA declares the city in violation of the federal Clean Air Act.  Despite deadlines, the EPA has refused to say whether Philadelphia has met a 2015 benchmark of 70 parts per billion or less of ground-level ozone in the ambient atmosphere.

The EPA was supposed to make its finding by Oct. 1. A federal court ruled this year that the agency, under its administrator, Scott Pruitt, broke the law by missing the deadline, and gave the EPA until April to make a decision.

In its new report, the association took issue with EPA efforts to roll back Obama-era rules.

"The American Lung Association in Pennsylvania calls on our members of Congress to defend the Clean Air Act, currently under threat from those who want to weaken this effective public health law," Stewart said. "We also call on the U.S. Environmental Protection Agency to implement and enforce the law instead of trying to roll back major safeguards such as the Clean Power Plan and cleaner cars, both steps that help us fight climate change and reduce air pollution."

On the positive side: Particulate pollution is getting better, most likely because coal plants are shutting down with the switch toward natural gas, the report says.  This kind of pollution is composed of soot, chemicals, and tiny particles emitted by coal-fired power plants, diesel fuel, and wood-burning fireplaces and stoves.  Wildfires can also cause spikes in particle pollution, which can affect respiratory and cardiovascular health.

The report found that "year-round particle pollution levels were all distinctly lower than in the 2017 report, continuing a steady decrease over at least six years."

Camden and Chester were among the nation's cleanest counties for particle pollution, with both earning an A.