Roadside Vegetables: Are they safe for consumption?

A blog by Bunmi.

On the outskirt of every major West African city I have been to - from Lagos to Cotonou, Lome to Accra - I have observed the growing tendency of concentrated, medium to large size, vegetable farms that produce varieties of vegetables to meet the demands of the city dwellers to dot the landscape.

I recall the good impression I had the first time I came across this type of vegetable farms along the Iyana Ipaja-Obadore-Ojo Expressway on the outskirt of Lagos Nigeria, in early 2008. Then, as recently graduated agriculturist, with focus on soil science, I thought it was great form of land use management, considering the land pressures - little land availability, competition for development purpose and infrastructures etc - and the massive, ever-growing population of Lagos which aggravates the land pressures.

But in recent times, with the benefit of more advanced education - mainly in the field of environmental biology/toxicology - I have come to realize the other, mainly negative, side of this kind of vegetable production that counterbalances the advantage of the good management of available land resources and raises the issue of public health concerns.

The issue is, these peri-urban farms are usually located along busy highways, with high-to-heavy vehicular movements, and the emissions from the exhaust of the vehicles passing by can lead to the deposition of harmful chemicals and toxic metals, chief among which is lead, on plants along the highways including those vegetables produced for human consumption.

The accumulation of lead in roadside soils and plants growing along highways varies with the traffic along such ways,research reportsindicate that up to 50% of lead released from vehicle exhaust isdeposited within 30metersof the road and the others scattered over a larger area of land.

Lead, a systemic poison, may accumulate to large amounts in plants beyond levels permissible for human consumption and thus have the tendency to build-up in these vegetables. Worse still, many plants, including popular Nigeria/West-African vegetables e.g. Celosia and Amaranthus, have the ability to accumulate large amounts of this toxic element without having any visible deleterious effect on their appearance or yield.

Lead poisoning can cause serious health effects in the human body, and ingesting it - in this case through vegetables - beyond level found to be permissible can result in health issues like nausea, anorexia and severe abdominal cramp, renal tubular dysfunction, muscle aches and joint pains, anaemia and weight loss. It can also pass through the placental barriers to cause miscarriages, abortions and stillbirths in pregnant women.

This contamination of roadside vegetables, with lead, is possible because of tetra ethyl lead (TEL) - a petrol/gasoline additive - often used as an anti-knock agent in petrol (or gasoline) used in vehicles which as a result makes the exhaust from automobiles rich in lead. Although, the use of lead additives in petrol/gasoline has been completely banned by law or significantly reduced in many developed countries, a lot of developing countries, Nigeria inclusive, still rely on leaded petrol to power vehicles on their roads.

On solution to this issue, therefore, is to avoid the use of petrol/gasoline with lead additives in Nigeria - and other West African countries where this form of vegetable production is practiced - but taking into consideration the history of petrol production/use in Nigeria and the cost involved in switching to new technologies, plus the time required to achieve all that, then that may not happen anytime soon.

So, for now, ensuring that leafy vegetable farms are moved away and far enough, from roads with heavy vehicular movements seems the better and ready available alternative. In their place, other crops or fruity vegetables - whose leaves or roots are not consumed (e.g. maize or okra) or crops not grown for human/animal consumption (e.g. cotton or kenaf) can be planted on the roadside plots to maximize the use of land.

That way, we can prevent negative public health situations and the breeding of chronic diseases among cities' populace while still getting as much as we can out of available land.

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