“Exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning…”
Amidst staggering mortality and morbidity rates due to malaria in the African continent, African Heads of State and Government have adopted the use of dichlorodiphenyltrichloroethane (DDT), a controversial chemical, as the means of eradicating malaria in the continent, This came after several debates which commenced Wednesday July 10 at a meeting of Health Ministers of various African countries; and continued at meetings of Ambassadors and members of the Permanent Representative Council of the African Union on July 12.
The final decision for DDT adoption was arrived at after another round of debate on Tuesday July 16, during a meeting of the African heads of state and government, which ended same day. However, long before its adoption by African leaders, concerns have been raised about the negative impact of the chemical on the health of humans.
DDT is a tasteless, colourless chemical that was successfully used in the second half of World War II to control malaria among civilians and troops. It was then regarded as a contact poison against several arthropods; hence, was also used as an agricultural insecticide, while its production and use skyrocketed.
The use of the chemical was first questioned by an American biologist, Rachel Carson, who wrote about the environmental impacts of the indiscriminate spraying of DDT in the United States and questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health.
The book, Silent Spring, published in 1962, suggested that DDT and other pesticides may cause cancer and that their agricultural use was a threat to wildlife and plants. Its publication birthed the environmental movement, and resulted in a large public outcry which
eventually led to DDT being banned for agricultural use in the U.S. in 1972. More than 600,000 tonnes were applied in the U.S. before the 1972 ban.
The chemical was subsequently banned for agricultural use worldwide under the Stockholm Convention, but its limited use in disease vector control continues till date, but remains controversial.
Notwithstanding the controversies, 3314 tonnes were produced in 2009 for the control of malaria.
In humans, medical researchers say it may affect health through genotoxicity or endocrine disruption. Genotoxicity involves the damage of the genetic information within a cell which then causes mutations, and which could lead to cancer. Further study results say it affects future generations of the primary affected person.
Endocrine disruption on the other hand involves negative interference of the hormone system in humans. These disruptions, results of medical researches state, can cause cancerous tumors, birth defects, and other developmental disorders. This specifically, could lead to learning disabilities, severe attention deficit disorder, cognitive and brain development problems; deformations of the body (including limbs); breast cancer, prostate cancer, thyroid and other cancers; sexual development problems.
Several African countries including Nigeria, however, argued that there were benefits in the use of the chemical.
Nigeria, South Africa others approve
Nigeria’s Minister of Health, Prof. Onyebuchi Chukwu, during the Abuja meeting, emphasized that the World Health Organization has cleared use of DDT in countries where mosquitoes are resistant to other insecticide, noting that the manner of usage is what matters.
“Some countries are using them. In the health sector, it’s to be used indoors, not outdoors. It is the Agricultural sector that doesn’t need DDT. We are not here for rhetorics but to seek the way forward and the summit and African Union is primarily for that purpose,” he stated.
Also, the South African representative reiterated that it is important for all African leaders to eliminate malaria in Africa, thus, queried
why DDT comes under attack annually whenever it is raised as a means of eradicating malaria.
“If we stop using it, we are sentencing our people to death. Every other continent used DDT to eradicate malaria, so why is our turn
different in Africa?”
He said that within five years, South African had a 600 per cent increase in malaria rate from 1996 when the country stopped using DDT.
“We had no choice but revert to it. DDT must remain here until a more effective chemical is discovered. We want to emphasize that it must not be removed from our agreed agenda on how to eradicate malaria in Africa,” he said.
The Commissioner, Social Affairs of the African Union Commission, Mustapha Kaloko, called for the inclusion of DDT as the means of
eradicating malaria in the region. He however noted that it is not to be generally used while food items must be covered and kept away and “only walls and ceilings are to be sprayed”.
“DDT will remain in the agenda as the major means for the eradication of malaria in the continent,” he said.
Consequently, all African leaders except Central African Republic which sent no delegate adopted the inclusion of DDT as the chemical to be used in eradicating malaria in the region.
Though DDT has been adopted by the African leaders as the key to eradicating malaria in the continent, fear still lingers even in
Nigeria as well as other African countries over its usage. Delegates who are against its usage were however scared of having their names in print when PREMIUM TIMES spoke to them.
One of the Nigerian delegates, who was against DDT being adopted, told PREMIUM TIMES that “I want malaria eradicated but I am really scared about the negative impact this would have on the health of Africans.
DDT is a renowned controversial chemical with grieve impact on health of mammals; and humans are at the worst receiving end.”
Other delegates from countries like the Republic of Chad and Mozambique equally shared same views as their Nigerian counterpart.
Effects of DDT on human health
Studies from the United States, Canada, and Sweden link DDT to diabetes; while the U.S. Environmental Protection Agency states that
DDT exposure damages the reproductive system and reduces reproductive success in humans. These effects, the agency says, may cause developmental and reproductive toxicity.
“Research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning … toxicological evidence shows endocrine-disrupting properties; human data also indicate possible disruption in semen quality, menstruation, gestational length, and duration of lactation” The Lancet- a science journal also states.
According to epidemiological studies on humans, exposure to DDT could also lead to premature birth and low birth weight, and may even harm a mother’s ability to breast feed.
Recently, other researchers from the United States, Canada, and Australia argued that these effects may increase infant deaths, thus,
offsetting any anti-malarial benefits.
A study carried out at the University of California, Berkeley, in 2006 indicated that children exposed while in the womb have a greater
chance of development problems, while other studies have discovered that even low levels of DDT at birth are associated with decreased attention at infancy as well as decreased cognitive skills.
In other related researches from around the globe, it was discovered that daughters of highly exposed women to this chemical may have more difficulty getting pregnant. This is called increased time to pregnancy, TTP, in medical parlance. Similarly, women who are exposed to the chemical in their first trimester of pregnancy (first three months) may have babies with retarded psychomotor development, while those who are unlucky could have a type of miscarriage called early pregnancy loss.
Also, occupational exposure in agriculture and malaria control have also has been linked to neurological problems such as Parkinsons and asthma.
More recent evidence from epidemiological studies, that is studies in human populations, indicate that DDT causes cancers of the liver,
pancreas and breast, while contributing to leukemia, lymphoma and testicular cancer.
DDT in the fight against malaria
Amidst latest progress reports that malaria incidence has reduced by one-third in Africa, the preventable but killer disease remains a
major public health challenge confronting the continent. As a result of this, public health officials rely on DDT to fight the disease due
to its ‘wonder working power’.
In the 1950s and 1960s, WHO’s anti-malaria campaign relied heavily on DDT and the results were promising, though temporary. Reviewing what went wrong, experts tied the resurgence of the disease to poor leadership, management and funding of malaria control programs; poverty; civil unrest; and increased irrigation.
Like Nigeria’s Minister of Health stated, the WHO in 2006, reversed a longstanding policy against DDT by recommending that it be used as an indoor pesticide in regions where malaria is a major problem. As of 2008, only 12 countries used DDT, including India and some Southern African states, as well as Namibia. With the African governments’ adoption of the chemical on Tuesday in Abuja, the number is expected to rise.
Effectiveness of DDT against malaria
When it was first introduced in World War II, DDT was very effective in reducing malaria morbidity and mortality. The WHO’s anti-malaria campaign, which consisted mostly of spraying DDT, was initially very successful as well. For example, in Sri Lanka, the program reduced cases from about three million per year before spraying to just 18 in 1963 and 29 in 1964. Thereafter, the program was halted to save money and malaria rebounded to 600,000 cases in 1968 and the first quarter of 1969. The country resumed DDT vector control but the mosquitoes had acquired resistance in the interim, hence, the country switching to malathion, which though more expensive, proved effective.
Today, DDT remains on the WHO’s list of pesticides. The world health body’s policy has shifted from recommending it only in areas of
seasonal or episodic transmission of malaria, to also advocating it in areas of continuous, intense transmission.
South Africa is one country that continues to use DDT under WHO guidelines. In 1996, the country switched to alternative insecticides
and malaria incidence increased dramatically. Returning to DDT and introducing new drugs brought malaria back under control.
Making a case for the pesticide, Namibia’s Minister of Health, Richard Kamwir, told PREMIUM TIMES that “DDT is effective against resistant mosquitoes. Mosquitoes avoid DDT-sprayed walls and this is what we used in my country. DDT is the best pesticide for malaria control as resistant mosquitoes avoid treated houses”.
He further argued that for the pesticide to be effective, at least 80 percent of houses in any vicinity must be sprayed if not, its
effectiveness would be jeopardized.
“People don’t like DDT because of the lingering smell and stains on the walls, but I can confidently tell you that it worked for us” he
When to use DDT
Many global research experts however urge that alternatives be used instead of DDT.
An epidemiologist, Brenda Eskenazi, said “We know DDT can save lives by repelling and killing disease-spreading mosquitoes. But evidence suggests that people living in areas where DDT is used are exposed to very high levels of the pesticide. The only published studies on health effects conducted in these populations have shown profound effects on male fertility. Clearly, more research is needed on the health of populations where indoor residual spraying is occurring, but in the meantime, DDT should really be the last resort against malaria rather than the first line of defense.”
Donor agencies against DDT usage
At the moment, the African continent is largely dependent on donor agencies for most of her programmes, including malaria control. As a result of this, there are fears that the decision to use DDT may witness some challenges.
It has been alleged that donor governments and agencies shy from funding DDT spraying, or make aid contingent upon not using DDT.
According to a report in the British Medical Journal, use of DDT in Mozambique “was stopped several decades ago, because 80 percent of the country’s health budget came from donor funds, and donors refused to allow the use of DDT.”
Before now, many countries had been under pressure from international health and environment agencies to give up DDT or face losing aid grants. Belize and Bolivia admitted to have given in to pressure on this issue from United States Agency for International Development, USAID.
The USAID has been the focus of much criticism. But the agency is currently funding the use of DDT in some African countries, though it did not in the past.
The Agency’s website states that “USAID has never had a ‘policy’ as such either ‘for’ or ‘against’ DDT for IRS. The real change in the
past two years (2006/07) has been a new interest and emphasis on the use of IRS in general – with DDT or any other insecticide – as an
effective malaria prevention strategy in tropical Africa.”
The website further explains that in many cases, alternative malaria control measures were judged to be more cost-effective that DDT
spraying, and so were funded instead.
The way forward
A WHO study released in January 2008 found that mass distribution of insecticide-treated mosquito nets and artemisinin–based drugs cut malaria deaths in half in Rwanda and Ethiopia- two countries with high malaria burdens. DDT, the study states, did not play an important role in mortality reduction in these countries.
Vietnam as well has enjoyed declining malaria cases and a 97 percent mortality reduction after switching in 1991 from a poorly funded
DDT-based campaign, to a program based on prompt treatment, bed nets, and pyrethroid group insecticides.
A review of 14 studies on the subject in sub-Saharan Africa, covering insecticide-treated nets, residual spraying, chemoprophylaxis for children, chemoprophylaxis or intermittent treatment for pregnant women, a hypothetical vaccine, and changing front–line drug treatment, found decision making limited by the gross lack of information on the costs and effects of many interventions, the very small number of cost-effectiveness analyses available, the lack of evidence on the costs and effects of packages of measures, and the problems in generalizing or comparing studies that relate to specific settings and use different methodologies and outcome measures. The two cost-effectiveness estimates of DDT residual spraying examined were not found to provide an accurate estimate of the cost-effectiveness of DDT spraying; furthermore, the resulting estimates may not be good predictors of cost-effectiveness in current programs.
However, a study in Thailand found the cost per malaria case prevented of DDT spraying ($1.87 US) to be 21 per cent greater than the cost per case prevented of lambda-cyhalothrin–treated nets ($1.54 US). Thus, casting some doubt on the unexamined assumption that DDT was the most cost-effective measure to use in all cases. The director of Mexico’s malaria control program found similar results, declaring that it is 25 percent cheaper for Mexico to spray a house with synthetic pyrethroids than with DDT. However, another study in South Africa found generally lower costs for DDT spraying than for nets.
A comparison of four successful programs against malaria in Brazil, India, Eritrea, and Vietnam does not endorse any single strategy but instead states, “Common success factors included conducive country conditions, a targeted technical approach using a package of effective tools, data-driven decision-making, active leadership at all levels of government, involvement of communities, decentralized implementation and control of finances, skilled technical and managerial capacity at national and sub-national levels, hands-on technical and programmatic support from partner agencies, and sufficient and flexible financing.