What are photochemical oxidants and ozone?
‘Photochemical oxidants’ is the technical term for the type of smog found in Australian cities during the warmer months of the year. This type of smog can be invisible or it can appear as a whitish haze. Photochemical oxidants are formed when sunlight falls on a mixture of chemicals in the air. Ozone is one of the main photochemical oxidants. Other chemicals such as formaldehyde are also found and, like ozone, have adverse health effects. Environment agencies measure the level of ozone because it indicates the total amount of photochemical oxidants in the air. Cities that have abundant sunshine over periods of time, together with moderate winds and high temperatures, are most likely to experience high levels of photochemical oxidants. Ozone is a gas that is formed when nitrogen oxides react with a group of air pollutants known as ‘reactive organic substances’ in the presence of sunlight. (See fact sheet on air toxics.) The chemicals that react to form ozone come from sources such as: m
