This implies implementing appropriate pollution control policies, technological progress, energy savings and environmentally sustainable transport policies. Progress can also be assessed against the health costs induced by degraded air quality and against domestic objectives and international commitments regarding air emissions and quality. Fine particulates (PM10) can be carried deep into the lungs where they can cause inflammation and worsen the condition of people with heart and lung diseases. Ozone (O3) is a photochemical oxidant, which causes serious health problems and damage to ecosystems, agricultural crops and materials. Human exposure to high 03 concentrations can give rise to respiratory problems and decreases in lung functions. Ground-level 03 is a ‘secondary’ pollutant: it forms when precursor gases (nitrogen oxides, volatile organic compounds, carbon monoxide, methane) come into contact in the presence of sunlight.