The Toxicity of the Vegetables we Consume Everyday

VEGETABLES have always been an important part of our meals on a daily basis bearing in mind their importance in terms of nutrients they provide to our bodies for growth and immunity against diseases.

Hardly do we ask ourselves as to the manner in which they are grown or prepared for the market. What matters, it seems, is to have them on the table.

But the findings of a recent study by the International Water Management Institute (IWMI) could make us think otherwise.

The study, whose report has just been released at the on-going World Water Week Conference in Stockholm-Sweden, revealed that waste water use was common in urban agriculture worldwide posing health risks to consumers.

“Waste water is widely used to irrigate urban agricultural land in developing countries, a practice that has both advantages and disadvantages,” the 53-city study reveals.

According to the report, waste water agriculture contributes importantly to urban food supplies and helps provide a livelihood for the poor, but can also lead to health risks for consumers, particularly for vegetables consumed uncooked or poorly prepared.

Waste water has a “large potential... for both helping and hurting great numbers of urban consumers,” IWMI researcher, Liqa Raschid-Sally, said during the global water conference.

The survey showed that 80 percent of cities studied were using untreated or partially treated waste water for agriculture posing serious health risks to consumers of the food produced.

“In over 70 percent of the cities studied, more than half of the urban agricultural land was irrigated with waste water and the same was being used primarily to produce vegetables and rice,” it says.

The report says that the practice is being used on 20 million hectares of land, especially in Asian countries like China, India and Vietnam, but also “nearly every city of sub-Saharan Africa and in many Latin American cities as well.”

In Ghana’s capital Accra, for example, which has almost two million inhabitants, some 200,000 city residents purchase vegetables each day produced on just 100 hectares of urban agricultural land irrigated with waste water, the report says.

However, the report did not call for a ban on the use of waste water, saying such a move could “adversely affect urban consumers, farmers and others who depend on urban agriculture.”

Instead, it urged local authorities to develop policies for safer waste water use, and advocated low-cost measures such as the use of drip irrigation, correct washing of produce, and waste water storage ponds to allow suspended solids to settle-out.

Perhaps it’s important to describe what waste water is so as to keep track of our discussion.

Waste water could be defined in terms of its source, composition, the manner of transmission or where it’s found.

This includes water transmitted through storm water drains and other similar channels. The source of this water in storm water drains can be from industries can be mixed with seepage water or even rain water.

It can also come from other activities such as car washing or food processing. Waste water also includes used domestic and sewerage water from houses and institutions.

All these ‘types’ of waste water carry different compositions (chemical and biological) some of which have the potential of posing health risks.

That’s why there have always been reports in the media raising concerns over the effects of urban agriculture especially vegetable growing to consumers of the produced food.

In March this year the Integrated Regional Information Network (IRIN), which is part of the United Nations Office for the Coordination of Humanitarian Affairs, reported from Dakar, Senegal that some of the vegetables sold in urban areas are toxic.

In the report titled ‘Toxic Vegetables for Sale’ quoted some vegetable growers in the city’s outskirts admitting that they were applying ‘dangerous’ levels of pesticides, fertilizers and other toxic substances such as waste water to improve the colour and growth of the crops.

“We (the cultivators) are…careless about people’s health. Even producers are not well protected,” IRIN quotes Babacar Wade, who was one of the farmers from Kounoune village, 40 kilometres east of Dakar.

He was growing lettuce, cabbage, parsley, aubergine, peppers, and okra some of the most coveted vegetables for export from Senegal, IRIN reported.

In the same story, IRIN quotes Amadou Diouf, an agricultural engineer who said such kind of the health risk was rife across the country.

“Some gardeners respect none of the health standards, they use waste-water or inappropriate pesticides at any dose and at any time. The risks are very serious for producers and consumers,” he said.

According to him, the toxicity levels that result can lead to “acute poisoning which can cause headaches, vomiting, anxiety, loss of sight, while chronic poisoning can cause toxicity, infertility in women and impotence in men.

As the report by the IWMI has indicated, this problem is common in most of our developing countries Tanzania not an exception.

In Dar es Salaam, for instance, many times environmentalists and health experts have raised concerns over the manner in which vegetables have been grown in the city.

In his study report ‘Managing Urban Agriculture in Dar es Salaam’, Camillus Sawio, from the Department of Geography of the University of Dar es Salaam besides underlining the importance of urban agriculture, cautions that some health risks are also involved.

According to him, urban agriculture (vegetable growing and livestock keeping) in the city was still rampant in hazardous areas and he cites Mzimbazi River Valley as a classical example.

“Msimbazi River is contaminated with heavy metals. Farmers in the valley irrigate crops with this contaminated water…,” Sawio says in the report.

The report shows a table that indicates the level of pollution of the river’s water with heavy metals such as lead, cadmium, zinc, copper and chromium.

Sawio says that the high quantities of the heavy metals in the river’s water especially lead and cadmium disqualify the water from being used for livestock consumption and irrigation purposes according to the provisions of the Water Utilization (Control and Regulation) Act of 1974.

“However, people continue to use the water for irrigation purposes and thereby aggravate health risks,” he says.

Indeed, many areas along the river’s valley such as Kigogo, Vingunguti, Hannanasifu, Keko, Sinza and Msimbazi vegetable growing is still rampant regardless of the health risks that such kind of agriculture poses to both consumers and the producers themselves.

This means that most of the vegetables (if not all) supplied in the city especially at the city centre and the neighbouring areas originate from the river’s valley.

Now the question is, how much has our health been affected by feeding on such vegetables everyday either at a restaurant during lunch time while at work or at home in the evening?

Sawio’s report emphasizes on the chemical contamination of the vegetables so grown. However, there are other health risks that are associated with vegetables produced in such circumstances.

Much of the waste water used for irrigation is contaminated with human waste that contains a number of diseases-causing germs including those responsible for the spread of water borne diseases such as cholera and typhoid.

It’s important to note that most of the vegetables reaching our tables are always not so much cooked so as not to lose their dietary benefits and hence the tendency has always been half-cooking them.

But this has its cost. Some of the microorganisms responsible for the spread of diseases can still manage to remain alive at such low temperatures and thereby pass on to the people consuming the vegetables.

No wonder cases of cholera outbreak in many areas of the country are commonplace every year mainly during rainy seasons. This doesn’t downplay other factors causing the diseases such as poor sanitation though.

For instance, the World Health Organisation (WHO) in its Tanzania Cholera Outbreak Profile of April this year reveals that between 2002 and 2006, most Tanzanian regions reported cholera cases and nine of the reported more than 2000 cases during the period.

The regions include Dar es Salaam, Dodoma, Kigoma, Lindi, Mbeya, Morogoro, Mtwara, Pwani and Tanga.

Now the challenge is on how to help urban food growers to treat waste water before applying it in their fields so as to prevent the spread of such preventable diseases. Allocation of enough land in safe and clean areas could also help to mitigate the problem.

As IWMI points out-out in its report, urban agriculture is there to stay hence the best option to go about it is to make it safer to the consumers and producers by taking the above alternatives into account.