Pirimiphos-methyl
is the active ingredient of a product called
Actellic which is manufactured by Zeneca. It is
used as a spray and a dust on stored grain to
kill insect pests. Actellic is the market leader
by a long way. The only other available products
are both OPs: Satisfar, based on the active
ingredient etrimfos, is made by Novartis; and
Reldan, based on the active ingredient
chlorpyrifos, is made by Dow Elanco. Reldan is
not a competitor in the real sense, because it is
only available as an emulsion for spraying on to
grain, and is not used as a dust.
Zeneca insists that Actellic
has been used all over the world safely for 25
years as an admixture on grain as well as in a
range of public health applications. The company
says Actellic has a low mammalian toxicity and
was only recently reviewed by the Pesticides
Safety Directorate and given a full label
registration.
But, and it is a very big but,
the evidence against using Actellic D is
persuasive. Three of the men profiled here either
say they have been made ill by the product or
that it is possible to store grain without using
it. A fourth will not use it on his wheat and
appears to have suffered no penalties from the
grain buyers as a consequence. Perhaps most
important of all, the Health and Safety Executive
(HSE) admits that it has monitored workers using
Actellic and found some evidence of 'significant
exposure' to OP chemicals. There is also evidence
that more and more insects are becoming resistant
to Actellic treatment (see box).
The obvious question is whether
it is right to go on using a product which may
damage human health, is not effective against
some grain pests, and can be avoided by
engineering changes to grain stores. This
question should be in the minds of members of the
Advisory Committee on Pesticides, who have been
asked by the Government to re-review all
anti-cholinesterase OPs, including
pirimiphos-methyl. To help the review process,
here are the experiences of three men who have
used pirimiphos-methyl and one who has avoided
it.
|
"I don't think protective clothing made any difference, I still had stomach upset, breathing problems, headaches, sweating..." |
Richard Bruce
Richard Bruce lives on
the Isle of Wight and has been diagnosed
with OP poisoning. He is sensitive to
light, perfumes and has lost the feeling
in his hands.
Before
1978, Mr Bruce used Actellic smoke and
wore very little protective clothing.
"I don't think it was a requirement
at the time." From about 1980,
Actellic was used to treat the barn walls
and surfaces because storage mites had
shown resistance to another product.
Actellic dust was used in grain fed to
the cows from 1985 until the herd was
sold in 1991. "I used Actellic on
the farm in a garden sprayer with a 12
foot pole to keep the spray away from me.
This was a liquid form used inside the
barn where we stored grain to feed to
cattle."
"We had problems with
resistant mites so we used to treat the barn
walls and surfaces with Actellic, the grain with
dust and every year we used the smoke to get into
the crevices which we couldn't reach with the
sprayer."
Once he was farm manager and
responsible for buying his clothing, Mr Bruce
"dressed up like a spaceman. I wore a
complete overall, carbon filter mask, a face
visor, goggles, rubber boots and rubber
gauntlets."
"I don't think protective
clothing made any difference because every year
we used the product, even though I was dressed up
like that, I still had stomach upset, breathing
problems, headaches, sweating and stuff like
that, but it was only a transient thing." Mr
Bruce noticed some odd effects on his heart
"in that it raced more than it should and I
was always carrying handkerchiefs because my nose
was running all the time. But you didn't put
those things down to the chemical because you
were always being told it was safe."
Gradually, over the years, Mr
Bruce said farmers were instructed by the
Government to ensure there was no insect
contamination of the grain. "ADAS (the
Agricultural Development and Advisory Service)
used to send out instructions on how to clean and
fumigate your barn and it was something everyone
had to do and still have to do now."
Most of the grain grown on the
farm was fed to the cattle. "Now I find it
difficult to hold a conversation for any length
of time if I have to concentrate as well. I very
rarely go out of the house because if I get a
touch of perfume I'm finished." Mr Bruce has
been diagnosed six times as having OP poisoning
and the condition has been written on sick notes.
"No less a person than the head of the
National Poisons Unit, Dr Glyn Volans, confirmed
that I should be treated as having been poisoned
by organophosphates. But unfortunately, on the
same day, he said he would withdraw that
diagnosis, so he's a bit confused."
 |
"An invitation to HSE to show us how to dust grain has been very curtly and abrubtly refused" |
Michael Pearce
Michael Pearce runs a
company specialising in the treatment of
stored grain, and lives near Yeovil in
Somerset. He has used Actellic, and says
current government advice about storing
grain is flawed and encourages use of the
chemical.
"The
present policy laid down by the Central
Science Laboratory that you trickle
ventilate from the bottom (of the stored
grain) pushing warm air to the top. This
is almost guaranteed in the average farm
situation to give you these pests."
Traps have been introduced to show where
the insects are, but Mr Pearce said you
could "almost guarantee" to
find them. "The whole thing has been
designed to manufacture a problem."
Most of Mr Pearce's
customers buying his services almost
never have to use any pirimiphos-methyl
or another product. "There is a long
history of very successful stores,
particularly in the brewing trade, where
no insecticide is either allowed or used
because all these problems can be
controlled by engineering."
There are two ways of
ventilating grain: either start at the bottom of
the stored heap and blow air to the top or take
it from the top and pull it out at the bottom.
"There is no doubt about it if you pull it
down from the top, the top stays dry, stays cold
and is totally inhospitable to roaming bugs and
they do not multiply there because the
temperature isn't right, and there is no water
and without those essential ingredients they
don't prosper. If you blow it, you provide those
things, you can't help it happening. Now this
argument has gone on for years, but the
interesting thing is that the people who do it
down and out don't get the problem: it's as
simple as that."
Applying Actellic dust to grain
is "a bit like putting stuff on your garden.
You have a bucket or container, good gloves and
you have to spread it around. It is very vague
and an invitation to HSE to show us how to do it
has been very curtly and abruptly refused.
"If you are in a store
with 15 feet high grain at a safe moisture
content, every time you put your foot down you
will sink nearly to your knees. It's a very
laborious business, and if you are wearing
protective gear and clutching your Actellic
container, it is very exhausting."
Mr Pearce remembers an
instruction from the Home Grown Cereals Authority
to farmers last year about applying Actellic and
digging it in. "Of course, the very thought
of that while wearing all those clothes is a
death sentence for someone like me who is a bit
over-weight and a bit elderly."
 |
"I have suffered increasing health problems associated with OP use" |
John Coyte
John Coyte farms near
Plymouth in Devon. He grew his own grain,
stored it, used Actellic and fed the
grain to his cattle. He has lost feeling
in the lower half of one of his legs and
has the symptoms of OP poisoning. "I
have used pirimiphos methyl in dust form
dating back to the years of imperial
measurement at seven ounces per tonne,
surface incorporated. But over recent
years I have suffered increasing health
problems associated with OP use."
"Following my problems with
exposure in July this year with full
safety gear, I removed all OPs from this
farm. I discussed my problems with Dr Tim
Marrs, senior toxicologist at the
Department of Health, regarding late
arrhythmias (heart disturbances)."
"I feel it is my duty to
point out to anyone using these chemicals the
risk to their health. I am concerned that higher
standards of treatment in grain stores will
persuade farmers to use increasing amounts
leading to low-level exposure and chronic ill
health."
Bob Wright
Bob Wright has an arable farm in a family
partnership near Leamington Spa in Warwickshire
where wheat, oilseed rape and linseed are grown.
Actellic has not been used on the stored wheat,
but Mr Wright has occasionally used Actellic dust
on stored rape seed to control weevils.
"Just over a year ago, the
first two loads of a 500 tonne contract of Riband
wheat were rejected by E.W. Berrows, the grain
storers, because it contained mites. We stored
the wheat for 16 months without putting any OP
chemical on it, and two months ago we sold it to
the maltsters Wallpole and Wright for £90 a
tonne. So we stored the same wheat in the same
building and achieved a premium on it without
using any chemical."
The secret to successful grain
storage is ventilation, Mr Wright said. He uses
on-floor drying and blows freezing air through
the grain once a fortnight during the winter. Mr
Wright bakes his own bread using flour from a
nearby mill, but he is not a convert to organic
farming. He avoids OP chemicals because he thinks
storage mites are resistant to the chemicals and
because there should be no OP residues in food.
Comment
In their last survey for the Ministry of
Agriculture, Fisheries and Food, which covered
the 1994 harvest going into 1995, the Central
Science Laboratory (CSL) found that about 12
tonnes of pirimiphos methyl had been used in farm
grain stores. In the survey before that covering
1990/91, the figure was about the same. Although
the figure for commercial grain stores varies, it
can be up to one tonne. There was a survey of
animal feed mills in England and Wales during
1991, but CSL staff regard the data as
incomplete. The only category not covered in any
detail is export grain silos.
Some of this tonnage goes
straight through into food. In 1993, 44 per cent
of samples of wholemeal bread contained residues
of pirimiphos methyl, and the equivalent data for
1996 still showed residues in 23 per cent of
samples.
Many arable farmers in England
and Wales will be members of the Assured
Combinable Crops Scheme which "... aims to
establish standards for the production,
harvesting, on farm handling and on farm storage
of combinable crops, cereals, oilseeds and
protein crops, and to verify producers'
compliance with them." In its first year,
the scheme has registered 5,081 members and 8,918
farms covering 2.7 million acres and 7.5 million
tonnes.
The scheme says that:
"Longer term storage (of harvested grain)
requires a specific storage strategy. The
temperature and condition of grain must be
monitored weekly... Appropriate corrective action
must be taken to remedy bird and rodent activity
and hot spots." But the scheme does not set
any engineering standards to help long-term
storage.
Evidence is emerging which
shows that people are allergic to storage mites,
whether alive or dead. It is unlikely that these
mites arrive from farms because most will be
removed during storage or by the grain buyers.
Mites have been found on supermarket shelves and
in kitchen cupboards. It is difficult for any
parent with an allergic child, for example, to
take action against any supplier because, unlike
other countries, the UK has not set maximum
levels for mite contamination in food.
As there is clear evidence that
Actellic causes illness and is ineffective
against many strains of mite, it should be banned
from use in agriculture. Farmers should be
clearly advised how to engineer grain storage
through the Assured Combinable Crops Scheme so
that they can avoid using any chemical if they
wish. One of the new Food Standards Agency's
priorities should be to set standards for storage
mites in food.
OP resistance extremely
widespread
A paper at the recent Brighton Conference may
have heralded the end of OP use in grain stores.
Dr Ken Wildey from the Central Science
Laboratory, a Ministry of Agriculture, Fisheries
and Food agency, reports finding 93% of strains
of flour mite surviving twice the maximum
approved dose of pirimiphos-methyl after 14 days
exposure in wheat. "Field populations of the
predominant storage beetle pest, the saw-toothed
grain beetle, are still likely to be controlled
by effective residual applications of pesticide
to stored grain, if the grain is stored
relatively warm," Dr Wildey has written.
"However, in the cooler conditions commonly
found in UK grain, disinfestation may not be
possible even using the maximum approved dose of
the market-leading grain protectant."(1)
Mites are highly allergenic and
have been found in 21% of cereal based foodstuffs
purchased at retail outlets in the UK.
OPs are simply not working.
Already, pest resistance has rendered older
organochlorines ineffective. Older OPs have
engendered resistance problems, and so now has
pirimiphos-methyl, the main active used.
Pyrethroids also provoke resistance.
There are no new molecules to
be used as magic bullets, and the current
alternatives are even more toxic. The fumigant
methyl bromide is an ozone depleter, and
phosphine is highly toxic to users.
If farmers and grain stores
continue using even higher doses of OPs, residue
levels in food will rise. The Pesticides Trust [now PAN UK]
is
asking the UK Working Party on Pesticide Residues
to monitor levels in cereal products in case of
this eventuality.
But are pesticides necessary in
grain stores? MAFF's own recent survey2 reports that 89%
of commercial grain stores used pesticides-and
11% used no pesticides. Organic farmers store
grain without pesticides. The main factors that
cause infestation in grain are to do with
temperature, humidity, ventilation and hygiene
coupled with closer monitoring of grain
condition. Finding mites in your breakfast
cereals may be the final proof that pesticides
provide no free lunch.
1. Wildey, K.B., Prickett, A.J., et al., The contribution of resistance in UK stored product pests to control failure and subsequent food contamination, The Brighton Conference: Pests and Diseases, British Crop Protection Council, Surrey, UK, 1998, Vol II pp.
2. Thomas, M.R.,Garthwaite D.G., et.al., Commercial Grain Stores in Great Britain, Pesticide Usage Survey Report 138, MAFF Publications, London, 1998, 20 pp, £3.
John Harvey is a broadcaster and writer on farming issues.
[This
article first appeared in Pesticides News No. 42,
December 1998, pages 12-13]