According to Kenya National Bureau of Statistics, there were 1.6 million cars on our  roads in 2011. National Transport and Safety Authority further records that between 2012 and 2016 nearly 1.2 million more vehicles joined our roads. It is, therefore, assumed that there are currently an estimated 2.3 million serviceable vehicles plying our roads. According to the UN Environment, vehicle population in Nairobi is expected to double in the next six years. While this is indicative of a growing middle class, it has also made Nairobi one of Africa's most polluted cities.

A major driving force behind this pollution is one that is most under-reported. Most motorists in Africa are unaware that the cars they are driving do not have the catalytic converter. This is a very important device that is found under the car within the engine exhaust system. It controls dangerous emissions by converting toxic gases into less toxic, breathable nitrogen and oxygen particles. It basically sieves out dangerous emissions so that we don't have to inhale them.

Regrettably, I dare state here that more than 60 per cent of the cars on our roads do not have this device. Since these converters contain palladium, platinum and rhodium, they are extremely popular in the black-market trade in Kenya and across the world. They are habitually and secretly cut off from our vehicles. This shocking act happens from our various garages through brokers who buy the parts for about Sh3,500 and thereafter export them to other global merchants for extraction of precious metals.

These metals are quite expensive. Platinum is currently selling for nearly Sh3.2 million per kilo, rhodium Sh3.3 million per kilo while palladium is currently fetching approximately Sh2.6 million per kilo. Due to the dynamism of the precious metal market, these three sometimes even fetch more than gold, hence the unending demand of catalytic converters in the black market.

Health is, however, infinitely more valuable than gold and all precious metals. According to World Health Organisation, air pollution levels in the world increased by eight per cent between 2009 to 2016. In Kenya, emissions from vehicles are a major contributor to air pollution that can cause several respiratory illnesses and cancer.

One way of tackling this increasing air pollution is to reduce the air pollution that comes from our vehicles. Accordingly, the catalytic converter must by law be a mandatory device in vehicles. The Government can support by zero-rating imports of these devices for a given period so that they can be more affordable for motorists to purchase locally. In addition, local credible and comprehensive roadworthiness vehicle inspection must be mandatory for private vehicles. It is also possible to regulate the export of such products to ensure that the catalytic converters are not removed from serviceable vehicles of unsuspecting motorists. That way, we will have cleaner air and healthier people. Think green, act green!

The writer is the founder and chairperson, Green Africa Foundation www.isaackalua.com