Allan Schapira writes a letter to the Lancet
DDT: a polluted debate in malaria control
A recent press statement from WHO about dichlorodiphenyltrichloroethane (DDT) and indoor residual spraying for malaria control [1] caused a considerable stir, despite the fact that, in terms of policy, it merely re-iterated WHO's endorsement of DDT as a useful insecticide for malaria control, albeit in a highly promotional way. In this recurring debate, arguments for and against DDT, as before, have been heated and mainly based on considerations far removed from the realities of malaria control.
That's because the press release misled by implying that WHO's policy had changed.
One group that criticised the WHO statement has inferred that my resignation from WHO's Global Malaria Programme in September, 2006, was related to my opposition to its promotion of DDT. [2] This assumption is erroneous. For many years, WHO's malaria-control professionals have fought hard against pressure from various sides to ensure access in malaria-endemic countries to DDT. [3] Hopefully, the statement now issued by the Global Malaria Programme [1] will put an end to this debate, so that all countries that need DDT for malaria control will have unfettered access to use it in accordance with WHO guidelines and with the Stockholm Convention on Persistent Organic Pollutants, if they are signatories to the latter.
Meanwhile, remarks from the opposite camp have not lacked passion, conveying the impression that large-scale use of DDT for malaria control, so long held hostage to misguided concerns for the environment, will now save the lives of millions of people from malaria. [4] This idea is not so simple. As pointed out in WHO's new position statement, indoor residual spraying is an effective intervention, provided a programme infrastructure can be set up and maintained to include trained sprayers, supervisors, managers, stocks, equipment, and vehicles, that roads allow access to every village at the right time at least once a year, and that insecticides are not diverted to agriculture. The need to prevent diversion has been highlighted for DDT, but for malaria control it is equally important for other insecticides. Furthermore, especially in areas with intense and perennial transmission, it is essential to maintain the population's long-term acceptance of spraying once or several times a year. [5]
While WHO's position statement makes it clear that DDT is no magic bullet, the press release rather gives the impression that it is.
In view of the difficulties encountered in maintaining indoor residual spraying, WHO has invested substantially in exploring other methods, especially insecticide-treated bednets. These nets have been effective in many rigorous trials, [6] especially to reduce childhood mortality in Africa. Few trials have compared insecticide-treated nets and indoor residual spraying, but results so far suggest that the methods are more or less equal in efficacy. [7] As pointed out by WHO,[8] the two methods are similar in the way they work, although unlike indoor residual spraying, insecticide-treated nets can protect individual users or households. Few data exist for the use and cost-effectiveness of combining these two methods. In view of the substantial costs of prevention for the huge populations at risk, national programmes will generally need to choose one of these two methods for a specific geographical area.
The choice of insecticide is secondary. Since only pyrethroids can be used for insecticide-treated nets, and pyrethroid resistance is emerging as a constraint on their effectiveness, [9] the fact that four classes of insecticides can be used for indoor residual spraying should be one of the main reasons justifying renewed interest in this method. In the choice between indoor residual spraying and insecticide-treated nets, a WHO study group convened in 2004 noted that the decision should, in most cases, be based on operational factors. [8] Because long-lasting insecticidal nets can be managed easily with minimum risk of diversion of insecticide, for most high-burden countries that have not developed an infrastructure for indoor residual spraying, the priority will be to ensure coverage of at-risk populations with such long-lasting nets. The renewed interest in indoor residual spraying could lead to interminable debates in countries about the pros and cons of DDT. Such discussions pit sectors against politicians when, in fact, a non-partisan commitment is needed desperately to protect individuals at risk of malaria with one of the two proven methods.
And this is the problem that pro-DDT groups like Africa Fighting Malaria cause. If a health organization decides that bed nets are more effective, AFM will attack them and accuse them of giving in to environmentalists.
I resigned my post as coordinator, vector control and prevention, of the Global Malaria Programme, WHO, on Sept 6, 2006, because of disagreements with the director of the programme about policy issues.
I'm guessing that the way Kochi threw Schapira to the wolves had something to do with this.
The DDT ban is a UNEP (environmental) initiative.
WHO (health) and FAO (agriculture) were always in favour.
Nope, UNEP seems to understand/accept the importance of DDT for indoor spraying:
Source
Hans, out of interest, are you still claiming the Stockholm Convention was responsible for a de facto ban in Tanzania?
Allan schapira has a new blog. It looks like it might be interesting for those involved in the DDT discussion. I remain curious about the politics of his leaving WHO. The text of the letter is there.
Thanks, Eli. I changed the link to go there.
Meyrick Kirby, yes because a country had to cut a lot of red tape to get an exemption. It wasn't the default option, you had to apply for it. And also of course there was a huge anti-DDT movement at the time.
So yes, a de facto ban is a good summary.
Hans,
You previously claimed there was a de-facto ban in Tanzania when you were there in 1998-2000. The Stockholm convention was signed in 2001. Unless the arrow of time is going backwards, the latter could not have caused the former.
Indeed you are correct: The Tanzania ban precedes the Stockholm treaty.
This is the timeline:
1962 Rachel Carson Silent Spring
1972 US DDT ban
1992 Tanzania DDT ban
1995 UNEP starts POP talks
2001 Stockholm agreement(exemption possible for malaria)
2004 World wide ban in force, Tanzania ratifies
2006 Tanzania lifts ban
So, there's a 30 year lag between Silent Spring and the Tanzanian ban and twenty year lag between the US ban and the Tanzanian ban - that's hardly screaming evidence of a causal link. There's also the counterfactual of the various countries that continued to use DDT for vector control.
Then two years after the "worldwide ban" Tanzania lifts its ban.
I like that hypothesis Ian, the Stockholm Convention, by underlining the importance of DDT for indoor residual spraying, has lead to countries lifting DDT bans worldwide. One for the UN there!
That should "led to countries lifting DDT bans" not "lead ...".
No it was agreed on the conference to make exemptions possible for DDT indoor spraying despite vigorous anti-DDT lobbying.
Thus it's not made easy for a country to use DDT, countries have to apply for exemption, so we are seeing a principle de jure global DDT ban. DDT bans are lifted for indoor spraying, thanks to WHO, not UNEP.
No Hans, countries do not have to apply for an exemption. Have you considered finding out what the treaty really says?
Here's some releavant text from STOCKHOLM CONVENTION ON PERSISTENT ORGANIC POLLUTANTS
http://www.pops.int/documents/convtext/convtext_en.pdf
Unfortunately, there is no Dutch version at http://www.pops.int/
Numbers 4 and 6 below are particularly pertinent to Hans' claim that "it's not made easy for a country to use DDT, countries have to apply for exemption, so we are seeing a principle de jure global DDT ban."
That depends.
Simply because a country has to submit information every 3 years about their use of DDT for disease vector control and have it evaluated by the Conference parties in consultation with WHO does not mean that there is "a de jure global DDT ban" in place or even that the Convention has imposed undue hardship on any country.
I would be curious how many of the countries who had "submit[ted] a report to the Secretariat justifying its continuing need for registration of that exemption" (as the Convention requires) had been denied their request to keep using DDT for disease vector control.
Perhaps Hans has information on this? I have no idea what the actual number of countries denied (if any) is, but I would simply say that it is highly relevant.
If few countries have ever been denied use of DDT for disease vector control under the Convention, for example, that would hardly be ringing support for the claim of a dejure (or even de facto) ban.
Text From the Convention below
Annex B
RESTRICTION
Part II
DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane)
1. The production and use of DDT shall be eliminated except for Parties that have notified the
Secretariat of their intention to produce and/or use it. A DDT Register is hereby established and shall be
available to the public. The Secretariat shall maintain the DDT Register.
2. Each Party that produces and/or uses DDT shall restrict such production and/or use for disease vector
control in accordance with the World Health Organization recommendations and guidelines on the use of
DDT and when locally safe, effective and affordable alternatives are not available to the Party in question.
3. In the event that a Party not listed in the DDT Register determines that it requires DDT for disease
vector control, it shall notify the Secretariat as soon as possible in order to have its name added forthwith to
the DDT Register. It shall at the same time notify the World Health Organization.
4. Every three years, each Party that uses DDT shall provide to the Secretariat and the World Health
Organization information on the amount used, the conditions of such use and its relevance to that Party's
disease management strategy, in a format to be decided by the Conference of the Parties in consultation with
the World Health Organization.
5. With the goal of reducing and ultimately eliminating the use of DDT, the Conference of the Parties
shall encourage:
(a) Each Party using DDT to develop and implement an action plan as part of the
implementation plan specified in Article 7. That action plan shall include:
(i) Development of regulatory and other mechanisms to ensure that DDT use is restricted to
disease vector control;
(ii) Implementation of suitable alternative products, methods and strategies, including
resistance management strategies to ensure the continuing effectiveness of these
alternatives;
(iii) Measures to strengthen health care and to reduce the incidence of the disease.
(b) The Parties, within their capabilities, to promote research and development of safe alternative
chemical and non-chemical products, methods and strategies for Parties using DDT, relevant to the
conditions of those countries and with the goal of decreasing the human and economic burden of disease.
Factors to be promoted when considering alternatives or combinations of alternatives shall include the
human health risks and environmental implications of such alternatives. Viable alternatives to DDT shall
pose less risk to human health and the environment, be suitable for disease control based on conditions in the
Parties in question and be supported with monitoring data.
6. Commencing at its first meeting, and at least every three years thereafter, the Conference of the
Parties shall, in consultation with the World Health Organization, evaluate the continued need for DDT for
disease vector control on the basis of available scientific, technical, environmental and economic
information, including:
(a) The production and use of DDT and the conditions set out in paragraph 2;
(b) The availability, suitability and implementation of the alternatives to DDT; and
(c) Progress in strengthening the capacity of countries to transfer safely to reliance on such
alternatives.
7. A Party may, at any time, withdraw its name from the DDT Registry upon written notification to the
Secretariat. The withdrawal shall take effect on the date specified in the notification.
In addition, the following from the main text of the Convention is also applicable:
"Prior to a review of an entry in the Register [of countries desiring exceptions], the Party concerned shall submit a report to the
Secretariat justifying its continuing need for registration of that exemption. The report shall be circulated by
the Secretariat to all Parties. The review of a registration shall be carried out on the basis of all available
information. Thereupon, the Conference of the Parties may make such recommendations to the Party
concerned as it deems appropriate."
Silly environmentalists - why lobby for a ban on a substance which we keep being told was already banned?