VEHICLES ON AIR POLLUTION
THE air that we breathe is composed of gases and particulates which when in their correct proportions do not pose any threat to our lives. Human activities, however, result in emissions which are termed anthropogenic sources of air pollution such as combustion of fossil fuels in industry and motor vehicles.
A marked deterioration in air quality has been noted in most urban settlements and industrialised areas including Harare. Broadly speaking, cars and trucks cause air pollution throughout their life, including air pollutants emitted during vehicle operation, refuelling, manufacturing and disposal.
Nationally, the number of vehicles has been increasing at an alarming rate in the past decade. Old or second-hand vehicles pose the greatest threat to human health as well as the environment as their combustion efficiencies are drastically low due to worn out mechanical parts and the absence of in built pollution abatement technology that is available in newer models.
Air pollution from cars and trucks is categorised into primary and secondary pollution. Primary pollution is emitted directly into the atmosphere while secondary pollution results from chemical reactions between pollutants in the atmosphere. These chemicals can cause mild to severe irritation to the eyes, nose, throat and lungs. They can also be absorbed into the body and cause deterioration in general health.
The extent of these detrimental effects on people’s health is related to the length of time one is exposed to vehicle emissions, the concentration of fumes breathed in and various other factors such as age and health status of the person exposed. The following are the major pollutants from motor vehicle exhausts: Particulate Matter (PM) Hydrocarbons (HC) Nitrogen oxides (NOx) Carbon monoxide (CO) Sulphur dioxide (SO2)
Greenhouse gases What is being done to curb air pollution from vehicles?
From 2014 to date, the Environmental Management Agency (EMA) conducted road blocks nationwide and performed roadside vehicle exhaust emissions tests and for each year compliance status was recorded. The owners of non-compliant vehicles were fined and the vehicles were compelled to be serviced. It is unfortunate that the proportion of vehicles whose exhaust emissions complied stipulated air emissions standards for Zimbabwe have been declining since 2014 to date. The implication is that more vehicles are polluting the air that we breathe. What Causes A Vehicle To Be Smoky? There are many reasons why a vehicle might emit continuous smoke:
spark plugs need replacement or cleaning ignition timing needs adjustment worn piston rings, pistons or cylinder bores worn valve stem guides or seals sump over-filled with engine oil blocked air cleaner
faulty electronic or mechanical controls in parts such as the choke poor, contaminated or incorrect density or grade of fuel blocked or damaged fuel filter
incorrectly set or damaged fuel injectors or fuel pump
Incorrectly set or damaged turbo or super charges.
What legislation governs atmospheric emissions?
Vehicle emissions are regulated in terms of the Environmental Management Act (Cap 20:27), sections 63-68 as read with Statutory Instrument 72 of 2009 (Environmental Management [Atmospheric Pollution Control] Regulations, 2009). The law stipulates the air emission quality standards permissible for various classes of vehicles and other auto mobiles focusing on parameters such as carbon monoxide, lead, nitrous oxides, particulate matter and sulphur dioxide. Recommendations to motorists Regular servicing of vehicles greatly reduces exhaust air pollutants as this facilitates better engine combustion efficiency. Even older vehicles can perform better when regularly serviced and worn out parts are constantly replaced with new ones.
Figure above: Proportions of vehicles whose exhaust emissions complied with Zimbabwean standards from 2014 to 2016, source EMA road inspection report