Given the great variety of substances present in the atmosphere, numerous classification methods have been proposed: firstly it can be classified according to the chemical composition, for which we mainly speak of compounds that contain sulfur, compounds that contain nitrogen, which contain carbon and halogen compounds.
econdly, it can be classified according to the physical state: gaseous, liquid or solid; finally, it can be divided according to the degree of reactivity in the atmosphere, into primary or secondary substances. The main effects that pollutants cause in the environment are the greenhouse effect, and acid rain, then of course they also lead to other problems such as the ozone hole and other less visible problems on flora and fauna.
The greenhouse effect: it is a climatic phenomenon that consists in the heating of the lower layers of the atmosphere, due to the shielding that some gases contained in it (greenhouse gases) offer, the latter are transparent to radiation of shorter wavelength and opaque to those with a wider wavelength, this means that the radiations with a shorter wavelength are able to cross these gases reaching the earth's surface, where they are partly absorbed and partly reflected; the absorbed part is released in the form of infrared which have a longer wavelength and therefore remain trapped by greenhouse gases.
The increase in the greenhouse effect following the industrial revolution was mainly caused by the release of fossil CO2 into the atmosphere.
The Cold Climate Impact on Air-Pollution-Related Health Outcomes: A Scoping Review, published on the International journal of environmental research and public health, analyzes: "In cold temperatures, vehicles idle more, have high cold-start emissions including greenhouse gases, and have less effective exhaust filtration systems, which can cause up to ten-fold more harmful vehicular emissions.
Only a few vehicle technologies have been tested for emissions below -7 ° C (20 ° F). Four-hundred-million people living in cities with sub-zero temperatures may be impacted. We conducted a scoping review to identify the existing knowledge about air-pollution-related health outcomes in a cold climate, and pinpoint any research gaps.
Of 1019 papers identified, 76 were selected for review. The papers described short-term health impacts associated with air pollutants. However, most papers removed the possible direct effect of temperature on pollution and health by adjusting for temperature.
Only eight papers formally explored the modifying effect of temperatures. Five studies identified how extreme cold and warm temperatures aggravated mortality / morbidity associated with ozon e, particles, and carbon-monoxide.
The other three found no health associations with tested pollutants and temperature. Additionally, in most papers, emissions could not be attributed solely to traffic. In conclusion, evidence on the relationship between cold temperatures, traffic-related pollution, and related health outcomes is lacking.
Therefore, targeted research is required to guide vehicle regulations, assess extreme weather-related risks in the context of climate change, and inform public health interventions."