Reaction with daylight ultraviolet (UV) rays and these precursors create ground-level ozone pollution (Tropospheric Ozone). Increases in ambient concentration come from primary anthropogenic pollutant precursor emissions, forest fires, and episodic stratospheric injection in the spring. However, the large amounts of NOX and VOCs released by human activities, such as the combustion of fossil fuels, has led to a large increase in the northern hemisphere background concentration. See the overview on Guide to Critical Loads and Levels. Woody vegetation is another major source of VOCs. We will take up Secondary air pollutants is the next post. Breathing in air that has ozone can harm human health. Other effects include slow growth in plants and increased risk of diseases, besides causing severe weather. Some migrates down from the stratosphere. The 10 Coldest Cities In The United States. Now let us read about some common primary air pollutants. This primary pollutant creates a reddish brown gas creating photochemical smog and tropospheric ozone. The gas can aggravate conditions of the lungs such as chronic bronchitis, asthma, and emphysema. Habitat quality and water together with nutrient cycles change due to ozone. Once inside the leaf, a series of chemical reactions occur leading to damage to cell membranes and other negative impacts on plant metabolism, including photosynthesis. Annual global fluxes of O3 calculated using a global chemistry–transport model have been included to show the magnitudes of the individual terms. Further reports and information are also available on the ICP Vegetation website. Photochemical reactions of NOx and VOCs (originating from largely from combustion processes) govern the concentration of ground-level O3 in the atmosphere. Classifying Pollutants • Haze Reduced visibility. However, the levels of indoor ozone are less than 50% of that found outside. A small amount of ozone does occur naturally at ground level. Bad ozone found at ground level, which is also known as tropospheric ozone or low level ozone is an air pollutant. The cause of the increases in background O3 are increases in precursor emissions throughout the northern hemisphere, including shipping, aircraft, vehicle, and industrial emissions in developing economies. But neither of these sources contributes enough ozone to be considered a threat to the health of humans or the environment. Days that are hot and sunny have higher concentrations of unhelthy ozone. This type of ozone has severe effects on health and the environment. Figure 3 shows the high background concentration in March to May over the northern half of Scotland, upland Wales and northern England, and parts of southern and eastern England. Most of the ozone that is found near the ground comes from vehicle exhaust and emissions from factories, power plants, and refineries. Exposure occurs both indoors and outdoors. Analysis and interpretation of 25 years of ozone observations at the Mace Head Atmospheric Research Station on the Atlantic Ocean coast of Ireland from 1987 to 2012. Pollutants involved in the creation of tropospheric ozone include emissions from industries, vehicles, and other sources of pollution. Ozone levels at a particular location may have arisen from VOC and NOx emissions many hundreds or even thousands of miles away. These emission controls have reduced peak ozone concentrations by typically 30 ppb in the UK, but over the last 20 years mean concentrations have been increasing in urban areas due to reductions in the local depletion of O3 by NO. Ozone (O3) is a key constituent of the troposphere. In contrast, O 3 in the troposphere (ground level) is regionally important as a toxic air pollutant and greenhouse gas. Ozone concentrations are highly variable, spatially and temporally. It does not have any direct emissions sources, rather it is a secondary gas formed by the interaction of sunlight with hydrocarbons – including methane – and nitrogen oxides, which are emitted by vehicles, fossil fuel power plants, and other man-made sources. O3 enters leaves via the stomatal pores on the leaf surface.