The exhaust emissions and gases are a mix of multiple particles and chemicals such as nitrogen oxide and carbon monoxide emitted by vehicles.
As a means of transportation, cars bring great convenience to people's travel, but their exhaust gas pollution to the environment has gradually become prominent, and the exhaust emissions has become an important source of urban air pollutants, but also endangering human health.
Where Does the Exhaust Emissions Come From?
Vehicles can be divided into gasoline vehicles and diesel vehicles according to fuel types.
The chemical composition of exhaust gas from fuel vehicles can reach 150 to 200 kinds, including gas and particulate matter.
Gasoline vehicle exhaust emissions are mainly gas and relatively less particulate matters, while the exhaust gas of diesel vehicles is mainly particulate matter, and the emission is 2-10 times that of gasoline vehicles.
The main components of vehicle exhaust emissions are carbon monoxide, hydrocarbons, etc. Among them, carbon monoxide is the product of incomplete fuel combustion caused by insufficient air or other reasons, while hydrocarbon is the unburned part caused by fuel evaporation and dripping in the oil supply system. It is a kind of brown exhaust gas with pungent odor produced in large quantities when the engine has a certain load.
According to statistics, every 1,000 liters of gasoline burned produces 360 kilograms of carbon monoxide, 2.4 to 4.8 kilograms of hydrocarbons, 6 to 18 kilograms of nitric oxide (NO), and about 3.6 grams of solid dust.
Therefore, the air pollution caused by huge gasoline consumption should not be underestimated.
In addition, diesel incomplete combustion will also produce a large number of black smoke, which contains unburned oil mist, carbon particles, some heterocyclic with high boiling point and aromatic hydrocarbon substances, such as the carcinogenic benzo [α] pyrene, which is harmful to human body.
The smaller the particle size, the more polycyclic aromatic hydrocarbon (PAHs) and heterocyclic compounds adsorbed, and the greater the impact on human health.
Diesel vehicle exhaust emissions are dominated by particulate matters with particle size less than or equal to 2 microns, which accounts for 60% to 83% of the total particulate matter, and the particle size greater than 2 microns only accounts for 17% to 40%.
The respirable dust with particle size below 5 microns can enter the alveoli and do great harm to human body.
Risks of the Exhaust Emissions
Diesel exhaust (2A) and gasoline exhaust (2B) have been classified as Group 2 carcinogens by the International Center for Research on Cancer (IARC), indicating the extent of their harm to human health.
The risks of carbon monoxide in vehicle exhaust emissions on human body is mainly manifested in the combination with human hemoglobin to form carboxyhemoglobin, which makes the blood flow lose the function of oxygen transmission.
The degree of harm depends on the concentration of carbon monoxide and the duration of exposure.
Nitrogen oxides mainly include nitric oxide and nitrogen dioxide, which are extremely harmful to human body, especially to respiratory system.
Exposure to nitrogen dioxide with concentration of 9.4 mg/m3 in the air for 10 minutes can cause respiratory system dysfunction.
Moreover, under the action of solar ultraviolet rays, nitrogen oxides and hydrocarbons will produce a kind of irritating light blue smoke called photochemical smog, which contains ozone, aldehydes, peroxyacyl nitrates and other complex compounds.
The most prominent harm of the photochemical smog to the human body is irritation of the eyes and upper respiratory mucosa, causing eye swelling and laryngitis.
Furthermore, photochemical smoke can also promote asthma attacks in patients with asthma, further aggravate chronic respiratory diseases, and may also play a certain role in inducing lung cancer.
Long-term inhalation of photochemical oxidants can affect the metabolism of human cells and accelerate human aging.
In addition, it causes serious damage to plants, reduces the visibility of the atmosphere, accelerates the aging of rubber products, corrodes construction equipment and clothing, and makes dyes fade.
Exhaust pollution has become an invisible "killer" of human health. It is particularly urgent to reduce vehicle exhaust emissions and achieve low-carbon life.