Pesticides and Public Health [Archives:1998/11/Health]

March 16 1998

Huge amounts of obsolete and unused pesticides continue to threaten human health and the environment in many developing countries. It is estimated that there are more than 100,000 tons of obsolete pesticide stocks in developing countries. These pesticides are often stored in leaking and corroding metal drums. If these stocks are located in urban areas or near water bodies, ground water, irrigation, and drinking water are at risk. According to FAO, only 1,511 tons have been disposed of in ten countries including Yemen.
The preferred way to dispose of obsolete pesticides is high temperature incineration. Safe incinerators are rare in developing countries. Unless prevention occurs, FAO warned, it is likely that accumulation of hazardous pesticides in the environment will continue unabated as the worldwide sales of pesticides increased substantially in 1995 and 1996.
Statistics issued by the Arab Organization for Agricultural Development indicate that Yemen has imported pesticides at a cost of $9,500,000 in 1991, $10,000,000 in 1992 and $1,250,000 in 1993. Yemeni farmers’ dependence on pesticides is increasing in such an uncontrolled way that it is negatively affecting both humans and nature. Presently, Yemeni farmers use about 34 different types of pesticides and agricultural chemical compounds.
Chronic Toxic Effects
Chronic effects of pesticides are not caused by direct exposure to large amounts of them, but the gradual, long-term intake of small doses. The effects of pesticides on the nervous system, especially their slowing the secretion of the choline esterase enzyme are discussed here. This enzyme coordinates the functioning of the muscles, the glandular system, and the nerve cells.
The organic phosphor and carbamatic compounds weaken the activity of this enzyme. The decrease in the choline esterase enzyme activity leads to toxic effects in the peripheral and central nervous systems and in all other systems of the body in which this enzyme is found. If they are not promptly treated, these effects can develop into chronic diseases that may eventually lead to death. 

Pesticides affect both humans and animals, according to the kind and degree of toxicity to which they are exposed. Long-term exposure happens to all people since they eat fruits, drink water, and even breath air polluted by pesticides. This causes chronic poisoning and here lies the danger.
A pesticide is able to accumulate in the body, and may lead to cancer or even make genetic mutations. The symptoms of poisoning by phosphor-based pesticides can be studied through determining the level of activity of the choline esterase enzyme in the blood.
The Yemeni-German project to protect plants made a field study in 1993 in Sanaa. The aim was to know whether using organic phosphor-based pesticides in Yemen results in serious pollution. In this study, several people from Aden, Al-Mahjal, Bait Al-Shatbi, Bani Hoshaish, Bani Al-Hareth, Hamdan, Ahdain, Raimat Hamad, Saber, Lahj and Sanaa were subjected to blood analysis. These analyses lasted for 25 days and their results are based as follows:
A. 100.0% – choline esterase enzyme is in its full activity.
B. 87.5% – the activity of the enzyme is down but still normal.
C. 75.0% – the activity of the enzyme is below normal.
D.50.0%-62.5% indicate that those people must totally avoid any more exposure to pesticides for two weeks and should wear masks while sprinkling pesticides in the future.
The study indicated that, generally, there is a widespread exposure to the phosphor-based pesticides. Most of the volunteers complained of suffering a lot from headache and fatigue after sprinkling pesticides. Of those, 13% suffered from full-blown illnesses. The final results of the analyses indicated that in more than 20% of them, the enzymes activity is below the normal level. For the other 28% of those analyzed, the enzyme’s activity was seriously down. The farmers and the pesticide- sprinkling staff (43%) as well as the qat chewers (32%) are the people who have the lowest enzyme activity.
The table above shows the results of the study concerning the level of the choline esterase enzyme activity for the different groups of people.
1- Abdullah Ali Al-Zora’i, Negative Effects of Pesticides, Sanaa 1996
2- Dr. Mohammed Al-Ghashm, Problems of Expired Pesticides.
Abdulqawi Abdulaziz,
Agricultural Engineer,
General Authority for Developing Northern Regions