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As Bill Chandler sees it, standing beside his sun-baked field of grapes
in the Central Valley of California, the people who want to get rid of pesticides
don’t understand farming. He says: ‘People in Los Angeles that wouldn’t
know a plum from a gooseberry are telling us that we’re doing things wrong
and accusing us, but how many people here have died from pesticides?’

Several hundred miles away in San Francisco, in the air-conditioned
offices of the Natural Resources Defense Council, an environmental pressure
group, Lawrie Mott insists that at least some of the chemicals that Chandler
uses shouldbe banned. ‘Qualitatively, we know that these substances are
human carcinogens,’ she says. ‘We know that they aredangerous. We know that
agriculture can survive withoutthese chemicals. Let’s just try to eliminate
their use.’

Chandler and Mott stand on opposite sides of a politicaldivide in California
that separates friends and foes of chemical pesticides. California is the
largest agricultural state in the US, with total farm sales of $19 billion
last year. It is also home to the country’s most vigorous environmental
movement. During last November’s state elections these two forces collided
in an expensive battle over agricultural chemicals. Besides the names of
candidates for local and national government, the ballot paper also contained
a proposal, known as Big Green, to ban at least 20 pesticides suspected
of causing cancer or damaging nerve cells in humans. It required chemical
companies to produce data proving that many more of their chemicals were
safe.

Big Green also included proposals to restrict commercial logging, oil
drilling and emissions of greenhouse gases, but its provisions on pesticides
generated the most controversy.

Environmental pressure groups think the laws on pesticides are too lenient
and full of loopholes, but voters in California seemed unconvinced that
additional regulations on pesticides were needed to protect their health.
They voted against Big Green on 6 November 1990 by a margin of nearly 2
to 1. The result pleased the chemical, oil and timber companies which spent
$16 million on a publicity campaign to convince voters that Big Green would
wreck the state’s economy.

But the environmental movement may still find that many pesticides disappear
from the fields-and the number could be 200 rather than 20, and not just
in California but throughout the US. The government’s Environmental Protection
Agency (EPA) is carrying out a review of all the chemicals currently approved
as pesticides in the US, and many are expected to disappear.

Although 80 per cent of the pesticides used in the US are herbicides,
most controversy surrounds insecticides, because they are generally more
toxic to humans and wildlife. Farm workers are the most directly affected.
California’s doctors reported between 2000 and 3000 cases of suspected poisoning
from pesticides each year during the 1980s. The problem may be greater because
many farm workers are migrants who sometimes speak little English, and many
victims may never see a doctor, says Ralph Leitstone, a lawyer who works
with the California Rural Legal Assistance Foundation. According to the
World Health Organization, workers in the developing world face higher risks
(Box 1).

Some of the most toxic insecticides, such as parathion, dimethoate and
acephate, belong to the organophosphate family of chemicals, which also
include the nerve gases tabun and sarin (Box 2). These chemicals block the
action of an enzyme called acetylcholin-esterase. This enzyme breaks down
the neurotransmitter acetylcholine after it has caused synapses to fire
signals to a variety of muscles, such as those controlling breathing and
the digestive system. Without the enzyme, the nervous system continues to
stimulate the muscles. In mild forms of poisoning a farm worker would experience
headaches, nausea and sweating. More severe doses can lead to loss of muscle
control, convulsions and even death. Just a few drops of parathion, absorbed
through the skin, can produce severe poisoning. Such severe cases are rare.
In California, one farm worker died last year from pesticide poisoning,
but in most years there are no deaths.

For people who do not work directly with pesticides, the risks are more
obscure. Most of the pesticides currently in use break down quickly into
nontoxic compounds when exposed to sun and rain, so few residues are left
by the time, say, fruit reaches the stores. Nevertheless, large numbers
of people are still exposed to small concentrations of pesticides on the
food they eat and in the water they drink. The EPA found traces from 109
different pesticides on food during a survey in 1989. This included residues
from pesticides not permitted in the US on imported pasta, lemons, pears
and other foods.

Some sampled foods contained no residues at all, and most contained
such small amounts that the agency did not consider them a hazard. The most
prevalent chemical in the EPA’s survey was malathion, the least toxic member
of the organophosphate family. According to the agency, a typical 15-year-old
would ingest 0.09 microgrammes of malathion per kilogram of body weight
each day. The EPA and the UN Food and Agriculture Organization have set
a standard for malathion of 20 microgrammes per kilogram per day. But when
the Natural Resources Defense Council added up the residues from all the
organophosphate pesticides found on raw food, it concluded that between
17 and 58 per cent of preschool children in the US consume more than the
standard permits.

In the ground, protected from the heat of the sun, many pesticides can
exist for months or years as they seep into the underground water table.
In California’s Central Valley, 1473 wells have been declared unsuitable
for drinking, cooking or bathing because of contamination with dibromochloropropane,
or DBCP, a chemical used in soil to kill tiny worms and fungal diseases.
The chemical was banned in 1979 after it was blamed for causing birth defects,
male sterility and cancer.

A survey in 1990 by the EPA found residues of pesticides in 10 per cent
of all community wells and in 4 per cent of all private wells. Wells, by
the way, account for about 40 per cent of all drinking water in the US.
Some of the pesticides the EPA found, such as chlordane, are no longer sold
commercially. The agency said that 0.8 per cent of all community water systems
in the US probably contain residues of at least one pesticide exceeding
the level that it considers safe.

No one disputes the presence of these residues, but controversy surrounds
the question of how dangerous they may be. Studying the health records of
people exposed to residues is not very helpful because the effects of the
chemicals are small and intertwined with other factors. So the EPA relies
on tests in which relatively large doses of a pesticide are fed to laboratory
animals. If these tests show that residues from a pesticide could increase
the risk of cancer by as much as one death in a population of one million,
the EPA has the power to restrict the use of that pesticide.

Bruce Ames, a biochemist at the University of California at Berkeley,
says that trying to eliminate such small levels of risk is foolish and expensive.
In a series of provocative articles, published last year in Science and
the Proceedings of the National Academy of Science, he produced calculations
showing that a person may consume 1.5 grams of natural toxins per day in
foods such as coffee, potatoes, tomatoes, whole wheat and brown rice. This
is about 10 000 times the average amount of pesticide residues consumed.
Only 52 of these natural toxins have been used in tests with animals to
see whether they cause cancer, says Ames. Half of them turned out to be
carcinogenic.

If more pesticides were banned, says Ames, cancer rates would go up
because far more cases of cancer result from bad diet than from residues
of pesticides. ‘The one thing we know is that we should be eating more fruits
and vegetables. If you ban pesticides, fruits and vegetables will be more
expensive, and people will buy less of them. The rich lawyers who are running
environmental organisations may not care, but the poor care,’ he says.

Lawrie Mott of the NRDC, who is not a lawyer but a biochemist, disagrees.
¿ìè¶ÌÊÓƵs have frequently been surprised to find hazardous levels of pesticides
in unexpected places, she says. Until about 20 years ago, scientists expected
pesticides to be filtered out by soil, or broken down by microorganisms
in the ground before they ever reached underground aquifers. By the 1970s,
however, pesticides started turning up in groundwater.

Nor are the safety regulations controlling the use of pesticides foolproof.
Aldicarb is a particularly toxic pesticide widely used on grapefruit and
oranges; in 1985, two growers broke the rules by deciding to spray watermelons
with it and 1000 people throughout the western US and Canada became seriously
ill. A few years ago, the manufacturer of an insecticide called propargite
added a new ingredient that caused the mix-ture to break down much more
slowly: 100 workers in California developed dermatitis after harvesting
oranges. The only way to prevent more unpleasant surprises, says Mott, is
to take the most dangerous pesticides off the market.

In 1988, Congress passed a law requiring the EPA tore-evaluate 600 chemicals
approved as pesticides in the US. Many pesticides were registered decades
ago when health standards were far more lenient. Manufacturers now have
to submit new studies on how their pesticides migrate through soil and air,
what products are formed when the chemical breaks down and how dangerous
they are to humans and other living organisms. Studies are required for
each crop on which farmers may use the chemical.

Reregistering all agricultural pesticides will probably take until the
end of the decade, but its impact is likely to be substantial for as many
as 200 of the 600 chemicals now in use are expected to disappear from the
marketplace. Most products are being withdrawn because chemical companies
are unwilling to spend money collecting data for older products that are
no longer protected by patents or that are sold in small quantities. ‘Most
of the decisions are based on economics, not on risk,’ says Susan Wayland,
who is coordinating the reregistration project for the EPA. Farmers growing
minor crops, like olives, brussels sprouts or pista-chios, may lose many
of the pesticides they now employ because companies make so little profit
from their small share of the market.

To help out the farmers, Frank Zalom, an entomologist at the University
of California at Berkeley, has put together an inventory of ways to produce
crops while using fewer pesticides. This approach, known as integrated pest
management, or IPM, acknowledges that pests often have natural predators
and parasites that keep them in check, and that disrupting this ecological
system with chemicals can do more harm than good. In the 1970s, for instance,
researchers discovered that one of the main pests in cotton, the bollworm,
could be kept in check by common mites. But California’s farmers were wiping
out these mites at the same time as they were ridding their fields of another
pest, the lygus bug. The result was a heavy infestation of bollworms. Growers
cut back their spraying and ploughed their cotton fields during the winter
to deprive the worms of their natural habitat. They now spray their fields
five times less frequently as farmers in other parts of the US.

Farmers used to heap scorn on IPM, saying that it really stood for ‘I
pay more’. But as pesticides come under increasing attack, many farmers
have changed their tune. ‘I’ve had more farmers contact me during the last
year, asking me how they can grow crops without chemicals, than I’ve had
in the previous 25 years combined,’ says Bill Barnett, who works at the
university’s Kearney Agricultural Research Station.

Farmers have discovered that relying on pesticides can be like stepping
onto an accelerating treadmill as more and more chemicals are required to
accomplish the same task. In some cases they do harm by killing off the
natural predators of the pests they are meant to destroy. ‘We loaded up
artichokes with parathion for years before we realised it wasn’t doing much
good,’ says Barnett. Parathion was supposed to control the artichoke plume
moth, but it was much better at destroying the moth’s natural enemies. As
a result, the moths returned quickly in greater numbers.

The more pesticides farmers apply, the more likely they are to create
strains of insects that can tolerate large doses of chemicals. Insects show
an astonishing ability to adapt to pesticides. In California, the pear tsylla
has become resistant to practically every pesticide that fruit growers have
used to kill it, including all organophosphate compounds. Efforts to eradicate
malaria from the world have foundered on the ability of mosquitoes to survive
large doses of pesticides. In 1946, only 12 cases of insects resistant to
a pesticide were reported. But by 1970 some 313 species had developed resistance
to at least one pesticide and by 1980 the number had risen to 829.

A resistant strain of insects is created, paradoxically, when pesticides
are too effective. The chemicals may kill off all insects except a tiny
minority that are genetically immune to their lethal action. These survivors
will breed only with each other, and all their offspring carry the genetic
ability to survive high doses of the chemicals.

In most cases, the exact mechanism of resistance to pesticides is not
known. In some, it may result fromgenetically determined differences in
behaviour; in others, resistant insects may have genes that create proteins
or nerve channels capable of overcoming the effects of pesticides that disrupt
the nervous system. Insects have to cope with toxic chemicals in many of
the plants they eat, so they produce a panoply ofdetoxifying enzymes.

In contrast, some of the IPM techniques are prosaic. Zalom encourages
farmers to pull out weeds instead of killing them with herbicides or to
change crops from year to year. Rotating crops deprives a pest of the habitat
in which it thrives, cutting its population dramatically. Other techniques
seem laughable. Planting marigolds may save potatoes from tiny worms called
nematodes; it seems that the worms hate the flower’s smell. Barnett and
Zalom have also been experimenting with insect scents, or sex pheromones.
Spraying an orchard with these pheromones confuses the male insects so much
that they cannot find females to mate with. Some researchers have organised
international expeditions to find the natural predators of insects that
migrated to California aboard aeroplanes and cars.

At Barnett’s agricultural research station, entomologists study insects
that live in an orchard of peach, almond and apple trees on which no chemicals
have been sprayed for 25 years. Barnett pointed out the damage to almond
nuts from the navel orangeworm, which migrated to California from South
America. In response, 10 years ago, researchers imported a natural parasite
of the orangeworm to control the pest. But Barnett had little success with
it until last year when damage from the orangeworm was almost completely
eliminated in one local farmer’s orchard. At last, he suggests, the parasite
has adapted to local conditions.

The most difficult problems to solve without resorting to chemicals
are plant diseases, says Zalom. For combating infections by microorganisms
there are few alternatives to commercial fungicides. If these chemicals
are banned, farmers may not be able to grow some crops, such as tomatoes,
all year round. For consumers, this means that fresh fruit will be harder
to find during much of the year-and more expensive.

The last word on whether farmers can afford to give up using pesticides
may come from consumers who demand perfect-looking fruit. Chandler has to
keep his peaches from being scarred on the outside by a small insect called
thrips, even though this damage is purely cosmetic. Barnett, in fact, looks
for fruit scarred by thrips when he goes shopping because the insect prefers
the sunlit south side of the tree, where the best-tasting fruit hangs. But
there are few shoppers like him. Barnett once displayed slightly damaged
fruit to a group of buyers for large grocery stores. ‘I asked ‘how much
of this fruit could you sell?’ They said ‘none’,’ recalls Barnett. ‘They
said consumers wouldn’t accept it.’

* * *

1: The hazards of using pesticides in the developing world

Pesticides may be worrisome in California, but they are a clear and
present danger in many parts of the world, particularly in developing countries.
In 1989, the World Health Organization estimated that pesticides poison
three million people each year, killing one in 14 of them. Even Bruce Ames,
who derides concern in the US about residues in food, says he was ‘appalled’
when he visited China. He said: ‘There were people working in clouds of
pesticides all the time, and they were using the dirtiest possible pesticides.’

There are no reliable statistics on the extent of pesticide use in the
developing world. Few herbicides are used in the tropics, because farmers
are likely to clear their fields of weeds by hand, so most of the chemicals
used are insecticides and fungicides.

Where farmers still grow traditional crops for themselves, old pesticides
like DDT are more commonly used because they are relatively cheap and available,
says Polly Hoppin, a researcher for the World Wildlife Fund. But when farmers
shift to growing non-traditional crops for export, they are generally provided
with newer pesticides, such as organophosphates and carbamates, that break
down more quickly. This is partly to avoid trouble with foreign customs
authorities: the US has begun to crack down on imported food that is contaminated
with pesticide residues. More modern chemicals also are more effective,
because many insects have long since developed resistance to DDT.

Even organophosphates and carbamates, when used heavily, have produced
strains of resistant insects, however. In the Dominican Republic, vegetable
farmers came to the brink of disaster in 1989 when two pests, a small insect
called Thrips palmi and the greenhouse whitefly, developed resistance to
several of these pesticides. According to Douglas Murray, a visiting researcher
at the Center for Latin American Studies at Stanford University, some farmers
used as many as seven different chemicals with little effect, sometimes
losing their entire crop. In May 1989, the US quarantined vegetable imports
from the country because they were infested with thrips. One local farmer
told Murray that a small spider had controlled thrips in previous years,
but that it had vanished, most likely the victim of heavy pesticide use.

Environmental groups blame development agencies such as the World Bank
for promoting agricultural projects that include large expenditure on pesticides.
Although the World Bank promised in 1985 to promote integrated pest management,
an analysis of bank lending by Michael Hansen of the Institute for Consumer
Policy Research in the US found that IPM was largely ignored. Projects in
Egypt and Yemen involved 10 and 20-fold increases in the use of pesticides,
reported Hansen. The World Bank itself has promised to adopt a far stricter
set of guidelines on pesticides during 1991.

The Food and Agriculture Agency of the UN has adopted a set of guidelines
for chemical manufacturers designed to reduce the misuse of pesticides.
Companies are supposed to put explicit warnings in local languages on the
labels of their products. Pesticides should come in small, ready-to-use
packages so that they do not have to be poured from one container to another.
The containers themselves should be designed to discourage reuse. Companies
are supposed to refrain from misleading advertising and to provide training
in how the chemicals are to be used.

The US Agency for InternationalDevelopment no longer finances any purchases
of pesticides abroad whose use is restricted in the US, but funding for
that portion of a project is often provided by other agencies or private
sources, says Hoppin. The practical impact of these measures on USAID’s
policy has been small: ‘They are still focused on managing the pesticides,
not managing the pests.’

Indonesia is blazing a trail in the opposite direction. In 1986 the
country’s rice crop was devastated by the brown planthopper, a small insect
that sucks juices out of the stem of rice. International agricultural specialists,
called in for advice, blamed the overuse of chemicals whose production was
encouraged with government subsidies of $50 million to $100 million each
year. The chemicals were wiping out a complex of spiders, beetles and parasites
that once kept the brown planthopper under control. As a result, the government
began to phase out 57 of the 61 most commonly used pesticides, including
all organophosphate chemicals. It ended subsidies for the others, increasing
their cost for the rice farmers.

Along with the ban, Indonesia started a nationwide programme to teach
farmers to monitor their fields for populations of dangerous and helpful
insects. The farmers learn to analyse the ecology of their own fields, drawing
diagrams that show which insects are pests and which creatures prey on them.
Many of the farmers that finish this training go on to train others. In
January of 1989, the full ban went into effect. So far the experiment seems
to be working, as harvests have been steady.

Molecular biologists are now trying to get plants to produce their own
pesticides. Several companies have transferred a gene from Bacillus thurengiensis,
a bacterium found in the soil, into tomatoes, maize and cotton. The gene
codes for a natural toxin that is lethal to such pests as the corn borer,
the cotton bollworm and the tomato fruit worm. The toxin has already been
sprayed on fields as a conventional pesticide. Plants that include this
gene and produce the toxin become poisonous to the worms.

At first glance this seems to be an ideal way of protecting crops. Seven
companies have already conducted field trials with crops that incorporate
the toxin-producing gene. But some scientists are worried that its popularity
will eventually render it useless, as pests develop resistance to it. In
Hawaii, several pests exposed to the toxin have already developed resistance.

* * *

2: Learning to live with hazardous chemicals

There is a great variety of pesticides on the market. A handbook of
agricultural chemicals published in the US lists nearly 500 of them and
most are sold under many different brand names. A few of them, such as nicotine,
have been used for more than a century, but the majority have appeared
within the last 50 years.

Pesticides are divided into herbicides, fungicides and insecticides.
Herbicides account for most sales in the US but, along with fungicides,
they have attracted less controversy than insecticides because most of them
are less poisonous to animals and humans. There are exceptions, however,
such as the highly toxic herbicides paraquat and dinoseb.

The earliest chemical pesticides were poisons found in plants. Farmers
spread their fields with nicotine from ground-up tobacco leaves, rotenone
from the roots of the derris plant, and pyrethrum, a mixture of chemicals
found in the painted daisy flower.

The first synthetic pesticide was a dye, called Paris Green which was
used on wallpaper and shutters, but mystery surrounds the circumstances
of its first use on crops. Robert Metcalf, an entomologist at the University
of Illinois, says that he tried to get to the bottom of the story, but all
he learned was that around 1865, ‘somebody dumped it on a potato patch and
discovered that it killed insects.’

The dye contained copper aceto-arsenite, which did not harm plants but
was lethal to insects. As a result, various compounds of arsenic soon became
popular insecticides.

Then, in 1939, came the revolution. Paul Mueller, a Swiss chemist, discovered
dichlorodiphenyltrichloroethane, or DDT. The chemical kills insects on contact
by disrupting their nervous system; at first, the poison did not seem toxic
to humans. DDT was hailed as a wonder chemical, and Mueller received a nobel
prize for his discovery in 1948. It was the first of a family of organochlorine
insecticides, so named because their chemical structure includes chlorine
atoms attached to rings of hydrogen and carbon.

Other organochlorine insecticides include aldrin, dieldrin and heptachlor.
Most of them were developed during the 1950s. They stay lethal for years,
which most people at the time considered a great virtue. That virtue turned
into a fatal flaw when scientists discovered residues of these compounds
building up in fatty tissues of other animals and even humans. Most organochlorine
pesticides cannot now be sold in the US and WesternEurope.

A second important family of insecticides, the organophosphates, emerged
from the chemical laboratories of Germanyduring the 1930s.

The first was parathion, followed by malathion, ronnel, dimethoate and
dozens more. Unlike organochlorines, these chemicals break down quickly
when exposed to the weather.

Unfortunately, they are generally more poisonous to mammals than organo-chlorines.
According to a survey of pesticides published by the World Health Organization,
113 milligrams of DDT per kilogram of body weight has a 50 per cent chance
of killing a rat. Only 3.6 milligrams per kilogram of parathion will have
the same effect. However, organophosphates are still the most commonly used
insecticides in the US.

A third class of insecticides, the carbamates, attack the same neural
pathways as organophosphates, but their effects wear off more quickly. As
a result, they are less dangerous to humans. Aldicarb is the most toxic
carbamate.

During the 1970s, the chemical industry introduced a new class of insecticides
called synthetic pyrethroids. These chemicals are similar to pyrethrum,
a natural toxin, but the synthetic versions are not supposed to break down
as quickly. They attack the nervous system, but no one knows exactly how
they work.

Pyrethroids are not very toxic to mammals, but they are lethal to fish,
so their use around streams, rivers and lakes is strictly controlled.