How is DDT used to fight malaria?

February 20, 2015

Can we dispel common misapprehensions about fighting malaria?

In fighting malaria, DDT is not used outdoors.  Spraying swamps with insecticide does little to combat malaria because malaria-carrying mosquitoes don’t usually breed or rest there, and collateral damage from DDT reduces mosquito predators.

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

USAID-paid workers conducting Indoor Residual Spraying (IRS) campaign. (Where? When?) USAID photo, via Stanford University, Human Biology 153

DDT’s utility in fighting malaria comes from its persistence when used close by humans bitten by those species of mosquito that carry malaria. Malaria is a parasitic disease.  Malaria parasites complete their life cycle in a human host (victim), and any insect taking blood from an infected human gets some of those parasites.  The parasite completes another phase of its life cycle in certain species of mosquito — not flies nor other biting insects — and after about two weeks, mosquitoes can infect humans with newly-ready parasites.

Those species that carry malaria are usually active from about dusk until after midnight.  Consequently, they bite people usually as they sleep.  Because the “blood meal” is heavy, newly-fed mosquitoes usually fly to a nearby wall of the home to excrete water from the meal, so they fly with a lighter load.  If DDT, or some other pesticide, coats that wall, the mosquito will die before being able to pass new parasites on to new victims.

DDT is NOT used to spray outdoors, to fight malaria.  Among other things, outdoor spraying threatens domestic animals and any creature that preys on the malaria-carrying mosquito; as a pragmatic matter, outdoor use affects only a tiny percentage of malaria-carrying mosquitoes. Malaria-carriers tend to breed in small, temporary pools of water from rain; this transience makes outdoor fighting difficult.  Many people fail to understand this crucial point: DDT outdoors doesn’t help in the fight against malaria.  (Other outdoor campaigns can provide relief, such as elimination of old tires, filling potholes in roads, draining raingutters, and generally eliminating the mosquito breeding areas close to human homes, since mosquitoes rarely move more than about 50 yards in their lifetime.)

It’s important to realize that DDT in IRS allows a mosquito a free first bite.  The hope is that bite is from an uninfected mosquito, who will then land on the treated wall of the home and get a fatal dose of pesticide, so that spreading malaria it may have picked up from its victim, is stopped.  Bednets, which form a physical barrier, prevent even the first bite.  Bednets gain effectiveness from treatment with impregnated insecticides.

The U.S. Centers for Disease Control, the lead agency in the campaign to eradicate malaria from the U.S. after World War II, explains this use of DDT in Indoor Residual Spraying, or IRS:

Indoor Residual Spraying

Many malaria vectors are considered “endophilic”; that is, the mosquito vectors rest inside houses after taking a blood meal. These mosquitoes are particularly susceptible to control through indoor residual spraying (IRS).

What Is Indoor Residual Spraying?

As its name implies, IRS involves coating the walls and other surfaces of a house with a residual insecticide. For several months, the insecticide will kill mosquitoes and other insects that come in contact with these surfaces. IRS does not directly prevent people from being bitten by mosquitoes. Rather, it usually kills mosquitoes after they have fed if they come to rest on the sprayed surface. IRS thus prevents transmission of infection to other persons. To be effective, IRS must be applied to a very high proportion of households in an area (usually >80%).

Health workers sparying insecticide on the walls of a wood and adobe dwelling.

Health worker spraying insecticide on the walls of a wood and adobe dwelling, in Indoor Residual Spraying (IRS). CDC image

History of IRS

IRS with DDT was the primary malaria control method used during the Global Malaria Eradication Campaign (1955-1969). The campaign did not achieve its stated objective but it did eliminate malaria from several areas and sharply reduced the burden of malaria disease in others.

Concern over the environmental impact of DDT led to the introduction of other, more expensive insecticides. As the eradication campaign wore on, the responsibility for maintaining it was shifted to endemic countries that were not able to shoulder the financial burden. The campaign collapsed and in many areas, malaria soon returned to pre-campaign levels.

As a result of the cost of IRS, the negative publicity due to the failure of the Malaria Eradication Campaign, and environmental concerns about residual insecticides, IRS programs were largely disbanded other than in a few countries with resources to continue them. However, the recent success of IRS in reducing malaria cases in South Africa by more than 80% has revived interest in this malaria prevention tool.

Rachel Carson understood this use of DDT, and she understood that outdoor use of DDT, such as crop spraying, or fighting insects affecting trees, could induce insects to evolve resistance and immunity to DDT.  In Silent Spring Carson warned that unless outdoor uses were greatly curtailed, DDT would be rendered ineffective to fight diseases.  Fred Soper, the super-mosquito killer from the Rockefeller Foundation who organized and led the UN’s malaria eradication effort, also understood the race against evolution of DDT resistance.  He had hoped resistance would not show up in tropical areas until the 1970s — malaria campaigns around the Mediterranean produced DDT resistance as early as 1948.  Sadly, resistance to DDT was already established in many mosquito populations in tropical Africa before Soper could take the UN’s program to them.  The UN had to abandon the campaign, as CDC’s explanation indicates.

Today, every mosquito on Earth carries some of the alleles of resistance to DDT, and many are immune to it.


Malaria fight, February 2015

February 20, 2015

Timely infographic from Agence France Presse.

Some background:  The newly-formed World Health Organization (WHO) estimated worldwide malaria deaths at more than 5 million per year, when it kicked off the ambitious but ultimately unsuccessful malaria eradication program in 1955.  Eradication hopes hung on the use of DDT, sprayed on the walls of homes in affected areas (Indoor Residual Spraying, or IRS), to temporarily knock down mosquito populations so that humans infected with malaria could be cured.  After early successes in temperate zones, malaria fighters took the fight to tropical Africa in 1963.  There they discovered that overuse and abuse of DDT had already bred mosquitoes resistant to the pesticide.  With no substitute for DDT available, WHO wound down the campaign on the ground by 1965, and officially abandoned it in 1969.

Nations who had pledged money for the fight early, cut back when DDT failed.  In 1963, about 4 million people died from malaria, worldwide.

Despite the lack of an international, worldwide fight against malaria, malaria fighters soldiered on.  Better housing and better medicines made gains.  By the time the U.S. banned DDT use on crops in 1972, pledging all U.S. production of DDT to fight disease elsewhere, annual malaria deaths had fallen to just over 2 million per year. By 1990, the annual death toll was cut to about a million per year.  Through the 1980s, malaria parasites themselves developed resistance to the main pharmaceuticals used to cure humans.

By the end of the 1990s, international agencies and especially NGOs like the Bill and Melinda Gates Foundation brought new funding and new urgency to the fight against malaria.  Expansion of production of artemisinin-based pharmaceuticals provided a new tool for health workers.  Funding from the U.S., through the President’s Malaria Initiative, helped a lot.  In 2000, about a million people died from malaria.  By 2014, malaria deaths fell to under 600,000.

Parasite resistance to the new pharmaceuticals poses a new threat to continued progress.  Funding is still far short of what experts estimate to be needed, and short of pledges from developed nations.  Mosquitoes that carry malaria parasites from human to human (after a step of the life cycle in infected mosquitoes) quickly evolve resistance to pesticides; malaria parasites develop resistance to pharmaceuticals used to treat humans.  Funding to rotate pesticides and drugs falls short, causing improper use of both, and quicker evolution of resistance in mosquitoes, and parasites.

Infgraphic from Agence France Presse, on the fight against malaria, February 2015.

Infgraphic from Agence France Presse, on the fight against malaria, February 2015.


Bill Gates agrees: We can eliminate malaria in a generation

January 9, 2015

Do we have the will to do it?

More:

Gates Foundation image:  A nurse dispenses a malaria drug to treat an infected child in Tanzania.

Gates Foundation image: A nurse dispenses a malaria drug to treat an infected child in Tanzania.


Want to do a good turn? Nothing But Nets needs you to save a kid from malaria. It’s cheap.

December 30, 2014

I get e-mail from the good people fighting malaria, those who can take your ten-spot and save an African kid from death by malaria.

Dear Ed,

We have 6,000 nets left to reach our 60,000 goal to protect refugee children and their families in Cameroon from malaria!

But I still need your last-minute help to hit our target before the December 31 deadline.

That’s why a generous donor has extended his extraordinary $500,000 matching gift campaign until midnight, December 31.

I can’t think of a more meaningful way to close out the year than by making a life-saving difference for $10.

Contribute now and your tax-deductible donation will have twice the life-saving impact and help Nothing But Nets and our UN partners protect refugees in Cameroon.

Doubled!

That means your year-end donation of $25 will be worth $50, and a generous gift of $50 will be worth $100.

Thank you for caring enough to help us defeat malaria and protect even more lives.

Chris Helfrich

Chris Helfrich
Director, Nothing But Nets

P.S. Please don’t wait another moment. Contribute now to our 60,000 net campaign for Cameroon and your donation will be matched by an extraordinary $500,000 matching gift provided by a generous donor—doubling the impact of your life-saving gift. Thank you for whatever you can afford.

Donate Now | View in browser

1750 Pennsylvania Avenue NW, Suite 300, Washington, DC 20006
© Nothing But Nets

$10 buys one net, delivered to a family in Africa, usually for a child. When the net is suspended over the bed of the child, mosquitoes cannot bite, and malaria transmission can be stopped. Nets help even if a kid already has malaria, because mosquitoes can’t bite him and get malaria parasites to spread.

Studies over the past 20 years show bednets alone are more effective than Indoor Residual Spraying (IRS), with DDT or any of the other eleven pesticides used.  To increase effectiveness, nets usually come impregnated with an insecticide, so mosquitoes that try to get to the sleeping people inside will die, too.

With the help of the Bill and Melinda Gates Foundation, millions of nets stopped malaria in its tracks in several different African nations; since the campaign got underway in earnest in 1999, malaria deaths have been cut by 45%, from more than a million each year in 1999 to fewer than 610,000 in 2013, according to the World Health Organization (WHO).

Malaria deaths declined from the 4 million per year at peak DDT use, circa 1958-63, to about 1 million per year in 1999 — a reduction of 75% from peak DDT use. Malaria deaths today may be the lowest in recorded human history.

Got $10 to save a life? Cut that death toll even further.


World Malaria Report 2014: Dramatic progress (no call for DDT)

December 9, 2014

World Malaria Report 2014 dropped this week.  It’s the annual report from the World Health Organization (WHO) on the fight against malaria, the problems, critical needs — and this year, wonderful news of progress.

Cover of WHO's World Malaria Report 2014, a child, and the red blood cells the malaria parasites attack.

Cover of WHO’s World Malaria Report 2014, a child, and the red blood cells the malaria parasites attack.

Copies of the report in .pdf format come in English, French and Spanish.  A host of supplemental materials and statistical compilations accompany the report every year.

The World Malaria Report 2014 summarizes information received from malaria-endemic countries and other sources, and updates the analyses presented in the 2013 report.

It assesses global and regional malaria trends, highlights progress towards global targets, and describes opportunities and challenges in controlling and eliminating the disease. The report was launched in the United Kingdom Houses of Parliament on 9 December 2014.

The press release on the report, from WHO:

Scale-up in effective malaria control dramatically reduces deaths

News release

The number of people dying from malaria has fallen dramatically since 2000 and malaria cases are also steadily declining, according to the World malaria report 2014. Between 2000 and 2013, the malaria mortality rate decreased by 47% worldwide and by 54% in the WHO African Region – where about 90% of malaria deaths occur.

New analysis across sub-Saharan Africa reveals that despite a 43% population increase, fewer people are infected or carry asymptomatic malaria infections every year: the number of people infected fell from 173 million in 2000 to 128 million in 2013.

“We can win the fight against malaria,” says Dr Margaret Chan, Director-General, WHO. “We have the right tools and our defences are working. But we still need to get those tools to a lot more people if we are to make these gains sustainable.”

Between 2000 and 2013, access to insecticide-treated bed nets increased substantially. In 2013, almost half of all people at risk of malaria in sub-Saharan Africa had access to an insecticide-treated net, a marked increase from just 3% in 2004. And this trend is set to continue, with a record 214 million bed nets scheduled for delivery to endemic countries in Africa by year-end.

Access to accurate malaria diagnostic testing and effective treatment has significantly improved worldwide. In 2013, the number of rapid diagnostic tests (RDTs) procured globally increased to 319 million, up from 46 million in 2008. Meanwhile, in 2013, 392 million courses of artemisinin-based combination therapies (ACTs), a key intervention to treat malaria, were procured, up from 11 million in 2005.

Moving towards elimination

Globally, an increasing number of countries are moving towards malaria elimination, and many regional groups are setting ambitious elimination targets, the most recent being a declaration at the East Asia Summit to eliminate malaria from the Asia-Pacific region by 2030.

In 2013, 2 countries reported zero indigenous cases for the first time (Azerbaijan and Sri Lanka), and 11 countries succeeded in maintaining zero cases (Argentina, Armenia, Egypt, Georgia, Iraq, Kyrgyzstan, Morocco, Oman, Paraguay, Uzbekistan and Turkmenistan). Another 4 countries reported fewer than 10 local cases annually (Algeria, Cabo Verde, Costa Rica and El Salvador).

Fragile gains

But significant challenges remain: “The next few years are going to be critical to show that we can maintain momentum and build on the gains,” notes Dr Pedro L Alonso, Director of WHO’s Global Malaria Programme.

In 2013, one third of households in areas with malaria transmission in sub-Saharan Africa did not have a single insecticide treated net. Indoor residual spraying, another key vector control intervention, has decreased in recent years, and insecticide resistance has been reported in 49 countries around the world.

Even though diagnostic testing and treatment have been strengthened, millions of people continue to lack access to these interventions. Progress has also been slow in scaling up preventive therapies for pregnant women, and in adopting recommended preventive therapies for children under 5 years of age and infants.

In addition, resistance to artemisinin has been detected in 5 countries of the Greater Mekong subregion and insufficient data on malaria transmission continues to hamper efforts to reduce the disease burden.

Dr Alonso believes, however, that with sufficient funding and commitment huge strides forward can still be made. “There are biological and technical challenges, but we are working with partners to be proactive in developing the right responses to these. There is a strong pipeline of innovative new products that will soon transform malaria control and elimination. We can go a lot further,” he says.

While funding to combat malaria has increased threefold since 2005, it is still only around half of the US$ 5.1 billion that is needed if global targets are to be achieved.

“Against a backdrop of continued insufficient funding the fight against malaria needs a renewed focus to ensure maximum value for money,” says Fatoumata Nafo-Traoré, Executive Director of the Roll Back Malaria Partnership. “We must work together to strengthen country ownership, empower communities, increase efficiencies, and engage multiple sectors outside health. We need to explore ways to do things better at all levels.”

Ray Chambers, who has served as the UN Secretary-General’s Special Envoy for Malaria since 2007, highlights the remarkable progress made in recent years. “While staying focused on the work ahead, we should note that the number of children dying from malaria today is markedly less than 8 years ago. The world can expect even greater reductions in malaria cases and mortality by the end of 2015, but any death from malaria remains simply unacceptable,” he says.

Gains at risk in Ebola-affected countries

At particular risk is progress on malaria in countries affected by the Ebola virus. The outbreak in West Africa has had a devastating impact on malaria treatment and the roll-out of malaria interventions. In Guinea, Sierra Leone and Liberia, the 3 countries most severely affected by the epidemic, the majority of inpatient health facilities remain closed, while attendance at outpatient facilities is down to a small fraction of rates seen prior to the outbreak.

Given the intense malaria transmission in these 3 countries, which together saw an estimated 6.6 million malaria cases and 20 000 malaria deaths in 2013, WHO has issued new guidance on temporary measures to control the disease during the Ebola outbreak: to provide ACTs to all fever patients, even when they have not been tested for malaria, and to carry out mass anti-malaria drug administration with ACTs in areas that are heavily affected by the Ebola virus and where malaria transmission is high. In addition, international donor financing is being stepped up to meet the further recommendation that bednets be distributed to all affected areas.

Note to editors

Globally, 3.2 billion people in 97 countries and territories are at risk of being infected with malaria. In 2013, there were an estimated 198 million malaria cases worldwide (range 124-283 million), 82% of which were in the WHO African region. Malaria was responsible for an estimated 584 000 deaths worldwide in 2013 (range: 367 000 – 755 000), killing an estimated 453 000 children under five years of age.

Based on an assessment of trends in reported malaria cases, a total of 64 countries are on track to meet the Millennium Development Goal target of reversing the incidence of malaria. Of these, 55 are on track to meet Roll Back Malaria and World Health Assembly targets of reducing malaria case incidence rates by 75% by 2015.

The World malaria report 2014 will be launched on 9 December 2014 in the United Kingdom Houses of Parliament. The event will be co-hosted by the All-Party Parliamentary Group on Malaria and Neglected Tropical Diseases (APPMG) and Malaria No More UK.

Contacts for press queries will be found at the link above.

Canadian-educated, Dr. Margaret Chan of the Peoples Republic of China heads the World Health Organization.

Canadian-educated, Dr. Margaret Chan of the Peoples Republic of China heads the World Health Organization, the world’s leading anti-malaria organization.

You may note that the press release says nothing about DDT, the pesticide most famous in the malaria fight after World War II.  WHO abandoned its ambitious campaign to eradicate malaria from the Earth, in the mid-1960s, when it was discovered that mosquitoes in central Africa and other malaria-endemic regions near the tropics were already resistant or immune to the pesticide.  DDT had been used by super-mosquito fighter Fred Soper, in campaigns by the Rockefeller Foundation and WHO, to knock down mosquito populations temporarily, to get breathing room to beat malaria.  While the populations were temporarily reduced, health workers would frantically work to diagnose and completely treat to a cure, malaria infections in humans. Then, when the mosquito populations came roaring back, the bugs would have no well of disease from which to draw parasites for new infections.

Soper’s methods used DDT sprayed on walls of homes, to specifically get those mosquitoes that bite humans. Anopheles spp. mosquitoes carry malaria parasites through a critical part of the parasites’ life cycle; those mosquitoes typically bite from about dusk to just after midnight.  After a blood meal, mosquitoes pause to rest on nearby vertical structures — walls in this case — to squeeze out excess water from the blood they’ve ingested, so they’re light enough to fly.  When the mosquito encounters DDT on the walls, the hope is that the DDT kills the mosquito, ending the transmission cycle.

A brutal public relations campaign in Africa, the U.S. and Europe through the late 1990s to now, has vilified science writer Rachel Carson for her indictment of DDT in Silent Spring, her brilliant book on the dangers of indiscriminate use of untested new chemicals.

So it’s important to note that the world’s leading organization that fights malaria makes no call for more DDT.  Professional health care workers worldwide have not been hornswoggled by pro-DDT, anti-environment, anti-science, anti-WHO propaganda.  That’s good news, too.

More:


Oh, look: EPA ordered DDT to be used to fight malaria in 1972!

October 29, 2014

U.S. Environmental Protection Agency did not start a “worldwide ban” on using DDT to fight malaria. EPA instead lifted a court imposed ban on use of the pesticide to fight disease.

At least a couple of times a week I run into someone who claims that environmentalists are evil people, led by Rachel Carson (who, they say, may be as evil as Stalin, Hitler and Mao put together), and that their hysteria-and-n0t-fact-based “worldwide ban” on DDT use led to tens of millions of people dying from malaria.

Each point of the rant is false.

air pollution control activities in the Four Corners area of the U.S., in the 1970s -- soon after the agency completed its hearings and rule making on the pesticide DDT.  EPA photo.

EPA Administrator William Rucklshaus during an airplane tour of air pollution control activities in the Four Corners area of the U.S., in the 1970s — soon after the agency completed its hearings and rule making on the pesticide DDT. EPA photo.

But lack of truth to claims doesn’t stop them from being made.

Serious students of history know better, of course.  Federal agencies, like EPA, cannot issue orders on science-based topics, without enough hard science behind the order to justify it.  That’s the rule given by courts, inscribed in law for all agencies in the Administrative Procedure Act (5 USC Chapter 5), and required of EPA specifically in the various laws delegating authority to EPA for clean air, clean water, toxics clean up, pesticides, etc.   Were an agency to issue a rule based on whim, the courts overturn it on the basis that it is “arbitrary and capricious.”  EPA’s 1972 ban on DDT use on certain crops was challenged in court, in fact — and the courts said the science behind the ban is sufficient.  None of that science has been found faulty, or the DDT manufacturers and users would have been back in court to get the EPA order overturned.

Reading the actual documents, you may discover something else, too:  Not only did the EPA order apply only to certain crop uses, not only was the order restricted to the jurisdiction of the EPA (which is to say, the U.S., and not Africa, Asia, nor any area outside U.S. jurisdiction), but the order in fact specifically overturned a previously-imposed court ruling that stopped DDT use to fight malaria.

That’s right: Bill Ruckelshaus ordered that use of DDT fight malaria is okay, in the U.S., or anywhere else in the world.

Quite the opposite of the claimed “worldwide ban on DDT to fight malaria,” it was, and is, an order to allow DDT to be used in any disease vector tussle.

How did the ranters miss that?

Here are the relevant clauses from the 1972 order, from a short order following a few pages of explanation and justification:

Administrator’s Order Regarding DDT

Order. Before the Environmental Protection Agency. In regard: Stevens Industries, Inc., et al. (Consolidated DDT Hearings). I.F.&R. Docket No. 83 et al.

In accordance with the foregoing opinion, findings and conclusions of law, use of DDT on cotton, beans (snap, lima and dry), peanuts, cabbage, cauliflower, brussel sprouts, tomatoes, fresh market corn, garlic, pimentos, in commercial greenhouses, for moth-proofing and control of bats and rodents are hereby canceled as of December 31, 1972.

Use of DDT for control of weevils on stored sweet potatoes, green peppers in the Del Marva Peninsula and cutworms on onions are canceled unless without 30 days users or registrants move to supplement the record in accordance with Part V of my opinion of today. In such event the order shall be stayed, pending the completion of the record, on terms and conditions set by the Hearing Examiner: Provided, That this stay may be dissolved if interested users or registrants do not present the required evidence in an expeditious fashion. At the conclusion of such proceedings, the issue of cancellation shall be resolved in accordance with my opinion today.

Cancellation for uses of DDT by public health officials in disease control programs and by USDA and the military for health quarantine and use in prescription drugs is lifted. [emphasis added]

In order to implement this decision no DDT shall be shipped in interstate commerce or within the District of Columbia or any American territory after December 31, 1972, unless its label bears in a prominent fashion in bold type and capital letters, in a manner satisfactory to the Pesticides Regulation Division, the following language:

  1. For use by and distribution to only U.S. Public Health Service Officials or for distribution by or on approval by the U.S. Public Health Service to other Health Service Officials for control of vector diseases;
  2. For use by and distribution to the USDA or Military for Health Quarantine Use;
  3. For use in the formulation for prescription drugs for controlling body lice;
  4. Or in drug; for use in controlling body lice – to be dispensed only by physicians. [emphasis added]

Use by or distribution to unauthorized users or use for a purpose not specified hereon or not in accordance with directions is disapproved by the Federal Government; This substance is harmful to the environment.

The Pesticides Regulation Division may require such other language as it considers appropriate.

This label may be adjusted to reflect the terms and conditions for shipment for use on green peppers in Del Marva, cutworms on onions, and weevils on sweet potatoes if a stay is in effect.

Dated: June 2, 1972

William D. Ruckelshaus

[FR Doc.72-10340 Filed 7-6-72; 8:50 am]
Federal Register, Vol. 37, No. 131 – Friday, July 7, 1972 pp. 13375-13376

Here is the entire order, in an image .pdf format.

More:


Rachel Carson: Pen Against Poison (U.S. State Department bio)

August 4, 2014

Especially for international audiences, often distributed by U.S. Embassies in foreign nations, the U.S. State Department offers a wealth of information about the United States, our businesses and heritage, and our history and national heroes.

For several years State has made available a 20 page booklet on Rachel Carson, one of the great drivers of the modern conservation movement after 1960. It was created in 2007, to celebrate the 100th anniversary of Carson’s birth.

Cover of the 20-page pamphlet, Rachel Carson: Pen Against Poison

Cover of the 20-page pamphlet, Rachel Carson: Pen Against Poison

It keeps moving.  Today I’m unable to find it at the site of the U.S. State Department, except through our Embassy to South Korea.  I fear the document may go away, and I frequently refer people to it.

I’m making it available here, as insurance against its going away from State Department sites.

If you haven’t read it, take a look.  If you’re a teacher of literature, or biology or science, or history, consider this as a resource for your students.

Three extended essays make up the substance of the book.  Phyllis McIntosh wrote, “A Quiet Woman Whose Book Spoke Loudly.”  Michael Jay Friedman discussed the effects of Carson’s work and writings, “A Book That Changed a Nation.”  And distinguished entomologist May Berenbaum contributed an essay on the actual controversies about the hard choices involved in dealing with pesticide safety, “A Persistent Controversy, A Still Valid Warning.”  There is a photo essay covering 50 years, and a series of links and other sources, good for students.

If you find those links no longer work, please comment below — and maybe send me an e-mail.

 

 


Follow

Get every new post delivered to your Inbox.

Join 2,665 other followers

%d bloggers like this: