Nitric oxide (NO) and nitrogen dioxide (NO2) are subject to the European Waste Incineration Directive, which puts strict limits on emissions to air. But removal of nitric oxide by incinerators is only about 60% effective and the remainder may be converted to nitrogen dioxide to form smog and acid rain.

Nitrogen dioxide has a variety of health impacts, such as higher incidence of respiratory symptoms in children, asthma, chronic obstructive pulmonary disease, lung cancer, heart disease in those over 65, and abnormally elevated immune and allergic responses. When nitrogen dioxide is combined with fine particulates and carcinogenic heavy metals (in particular cadmium), the effects on lung cancer are likely to be more potent.

Incinerators may emit fine particles, and the EU Waste Incineration Directive puts limits on emissions to air of heavy metals, dust, and total organic carbon, among other pollutants. Therefore, incinerators operate a filtration system to control particulate emissions.

PM₁₀ is defined as the mass of particles of less than about 10 microns (or one-hundredth of a mm) in diameter per cubic metre of air. PM_2.5 is the mass of particles of less than about 2.5 microns in diameter per cubic metre of air. PM₁₀ and PM_2.5 samples from around the world can vary substantially in their chemical composition and size distribution, and it is possible that associated metals and ultrafine particles are important. Yet international and national regulations are currently framed in terms of mass concentrations instead of, say, the chemical (metallic) composition, the number of particles and total surface area of particles per unit volume of air, or the capacity of particles to generate free radicals.

Long term exposure to particles affects the risk of mortality, especially from cardiovascular disease and from lung cancer. Short-term increases in concentrations cause increases in deaths from and hospital admissions for heart attacks and respiratory disease, and related symptoms.