Examination of Witnesses (Questions 300-316)
21 FEBRUARY 2004
PROFESSOR DAVID
COGGON AND
PROFESSOR DAVID
FORMAN
Q300 Chairman: There is another area
of uncertainty, is there not, and that is the ACP's medical and
toxicology panel, which considers the review of literature concerning
an association between Parkinson's Disease and pesticides. Professor
Coggon, would you like to take us briefly through your conclusions
of that review?
Professor Coggon: Yes. In many
ways, the situation parallels that for prostate cancer. We have
a systematic review, in this case actually commissioned at the
request of the ACP, carried out by the Institute for Environment
and Health in Leicester, looking at epidemiological studies of
the relationship between Parkinson's Disease and exposure to pesticides,
and also briefly reviewing the relevant toxicology. There are
quite a number of studies in the literature, more than 40, and
as we suspected when we commissioned the work there are more showing
a positive association between Parkinson's Disease and pesticides
than you would have expected if the whole thing was left to chance.
Again, the relative risk is not that high if you look at them
overall. The pattern is not entirely consistent. There are a surprising
number that show positive relationships, but it is not entirely
consistent. There are some that show inverse relationships with
a lower risk of Parkinson's Disease in people exposed to pesticides.
There is not any evidence pointing consistently to a problem with
any single pesticide or class of pesticides. The question is,
is the association a causal relationship with one or more specific
pesticides? Is it due to biases in the way in which studies have
been carried out? A particular problem in this context is that
many of the studies are case-control studies, where you start
with a group of patients who have Parkinson's Disease, and a group
of controls that do not have the disease, and ask them about their
past exposure to pesticides. When you do studies like that, quite
naturally the patients that have the disease that is under investigation
are more motivated to recall past exposures than the controls
are, and so you can get a spurious association between exposure
and disease when you do that sort of study. You can also get biases
from selective publication, because people do a case-control study
of Parkinson's Disease and look at a whole lot of different environmental,
dietary and lifestyle exposures, but then they only publish the
ones that look interesting and positive and not the ones that
do not look so interesting; so when you just look at the information
that is in the published literature, you get a biased view. That
is a possible explanation; or there could be one or more pesticides
there that are causing Parkinson's Disease, and it has not been
picked up on the extensive toxicological screening that is carried
out for pesticides. When you look at the toxicology and neuro-toxicity
that is assessed as part of the registration process for pesticides,
you do not find indications of pesticides causing damage to that
part of the brain that is affected in Parkinson's Disease. You
have to keep an open mind on this. In a way, it is more difficult
to investigate further than prostate cancer because in prostate
cancer you can use mortality from the disease as an outcome measure.
It is fairly reliable as an index of prostate cancer; whereas
for Parkinson's Disease, as you know, many patients die of other
causes, and Parkinson's Disease does not get on to the death certificate
necessarily. It may get on differently in some people than others,
and that can give rise to misleading results when you do epidemiological
studies. There is in this case quite a lot of ongoing research
both in this country and in other parts of the world. We have
decided that while it is not appropriate to take any regulatory
action at this stage in relation to Parkinson's Disease and pesticides,
there is again a need to keep a watching brief on what is coming
out in this area. We have recommended that further work be commissioned
looking at the mechanisms of toxicity that might underlie a link
between chemicals and Parkinson's Disease, because if we had a
clue that one particular pesticide or group of pesticides might
be responsible, then we might be able to commission epidemiological
research looking particularly at that group of pesticides.
Q301 Chairman: Who will pay for any research,
of whichever kind you might undertake?
Professor Coggon: If it is generic,
then it will come from government, by Defra. If it is specific
to a single product and it is required in order to support the
approval of that product, then it will come from the manufacturer.
It is unusual for us to request epidemiological studies from approval-holders,
but we have done it in the past where there was a particular concern
that could be addressed by an epidemiological investigation.
Q302 Chairman: Are you making specific
request now, or is it a recommendation? How far have you got in
regard to nailing down future work?
Professor Coggon: We have made
a recommendation, and my understanding is that that work is being
commissioned, but I think you would need to ask Defra where they
have got to with that.
Q303 Chairman: We will have that opportunity!
In the light of the diseases we have spoken of, does all of this
suggest to you that there ought to be the application of a precautionary
principle in the use of pesticides because of these uncertainties?
Professor Coggon: We already apply
a very precautionary approach in the regulation of pesticides,
and by that I mean that we make allowance for uncertainty. We
do not wait until there is evidence of an adverse effect before
we react to restrict the use of a pesticide; the reverse is true.
There has to be positive evidence that there will not be adverse
effects before a pesticide is allowed on the market. The regulation
of pesticides is much more precautionary than for most other chemicals
in the environment and in the workplace. The comparable group
would be medications, and there are very good reasons for that;
of their nature, pesticides and medicines are biologically active,
and therefore intrinsically they are more hazardous materials
than most other chemicals. The approach to regulation has become
increasingly precautionary over the years, which is the main reason
why a lot of the older products have disappeared from the market;
either they do not meet current standards, or more often because
the manufacturers make a commercial decision not to generate the
information that would be needed to meet modern standards.
Q304 Chairman: Perhaps because we know
they have been causing problems.
Professor Coggon: I do not think
it is because of an awareness that they are causing problems;
I think it is a commercial decision, that if you want to retain
approval for this chemical, you will have to provide the following
studies in addition to the ones you already have, and that will
cost you a lot of much money, so how much profit can you make
from this chemical, and is it worth the effort? I cannot recall
any pesticide being withdrawn from the market in the time that
I have been involved in the Advisory Committee on Pesticides because
there was evidence that it was causing harm to people.
Q305 Chairman: I am thinking about before
you were in your job, about DDT and things like that.
Professor Coggon: DDT and the
organochlorines have gone principally because of concerns about
the environment and about the persistence in the environment,
not because they have been shown to be causing adverse health
effects, or not as far as I am aware anyway.
Chairman: I think we might dispute that,
but we will not do so now.
Q306 Paddy Tipping: I want to ask you
about the incidents of breast cancer in the UK. In most industrial
countries it seems to be rising and there have been suggestions
that pesticides are associated with this. What is the evidence?
Professor Forman: Breast cancer
has increased. It is not increasing as fast as you might sometimes
believe from some of the media stories, especially when one takes
into account the impact of mammographic screening, which we have
now had in this country for 15 years or so. The causes of breast
cancer are a little bit better understood than those of prostate
cancer, which does not actually indicate a lot. However, we do
know that a number of reproductive factors like the number of
children, age of menarche and so on influence the risk of breast
cancer quite profoundly. I would agree with you that there has
been a concern that pesticides might be involved in the aetiology
of breast cancer. Most work has been conducted on the organochlorine
insecticides. In fact, there has been a large volume of research
on that particular class of pesticides. The Committee on Carcinogenicity
has looked at that evidence on a number of occasions and reported
most recently, in the middle of last year. That included substances
such as DDT and its derivatives. Although we were discussing earlier
what it takes in order to provide absolute reassurance, the evidence
on DDT and breast cancer, when you consider it in the round, is
about as reassuring as it could be in the sense that if you take
all the studies together there is absolutely no evidence of hazard
associated with exposure to DDT, and that is using very good indicators
of exposure, not the memory recall type of information, but blood
measures of the substance and its derivative, which is long-lasting
in the circulatory system. The Committee on Carcinogenicity looked
at a number of the different organochlorine insecticides, and
although not all of them had a lot of evidence associated with
them, by and large there was relatively little cause for concern.
There was one particular organochlorine, dieldrin, for which there
is only a small amount of evidence available—from memory
only two or three studies have been conducted. Those studies conflicted
amongst themselves. The evidence around DDT and its derivative
DDE certainly showed in aggregate a large body of data that came
down to a conclusion of no evidence of harm.
Q307 Mr Wiggin: To what extent would
a Government admission that pesticides had been causing health
problems lead to claims for state compensation?
Professor Coggon: The grounds
for state compensation, I guess, would be that the Government
had required people to use pesticides—so it might be an
issue in relation to sheep dip, which does not get regulated as
a pesticide but gets regulated separately—or that the regulatory
process, and my committee, had not done their job properly. Certainly,
I have been approached in the past by lawyers who were thinking
about taking action against the Committee for Safety of Medicines
because they felt they might have acted earlier in relation to
a concern about a drug. Those are two mechanisms whereby people
might make a claim against the Government.
Q308 Mr Wiggin: To what extent does the
legal liability rest with the manufacturer for ensuring their
products are safely used?
Professor Coggon: I am not a lawyer,
so I would hesitate to answer that question—I would probably
get it wrong.
Q309 Mr Wiggin: One of the reasons for
pushing you on this is because legal measures will be introduced
requiring farmers to keep records of pesticides and to make those
records available to the public via a third party, and so you
can see that that is likely to generate this type of inquiry.
Professor Coggon: I am not a lawyer,
but I guess for the farmer the parallel would be the doctor who
prescribes a medicine that is approved for use. If a farmer uses
a pesticide in an approved manner and is then subject to a claim
from a member of the public because it turns out that the pesticide
is not as safe as everybody thought it was, I would have thought
the farmer was in the same position as the doctor. I am not a
lawyer, as I say.
Q310 Mr Wiggin: I think that is a very
helpful answer though, because obviously we are looking at the
Voluntary Initiative and what scope there is for improving it
and addressing these health concerns, and whether or not that
is one of the things that would be helpful we value your views
on.
Professor Coggon: Any improved
training of operators has potential benefits in terms of minimising
mishaps when pesticides are being used. We know that a small number
of accidental pesticide poisonings do occur each year. In fact,
we are doing an investigation of them at the moment sponsored
by the Department of Health. From the initial findings, a substantial
proportion of them—it is based on rather small numbers—seem
to be from mishaps that occur while people are handling pesticides
and they get splashed or something like that. If people are better
trained and know how to use the equipment that they are provided
with, then the risk of that sort of thing happening should be
reduced.
Q311 Mr Wiggin: From what you have said,
which I am sure the Committee is very grateful for, it seems to
be that because of your committee the products are safe. If people
do not use them properly and do the right thing, then potentially
there are serious repercussions, whether it be a type of cancer
or other sorts of damage. In which direction should we be pushing
the operators? Training is one thing, but legislation would not
necessarily stop you getting splashed.
Professor Coggon: It is a question
of balance. First of all, I should correct you—we cannot
say that pesticides are safe, and we should avoid that term. We
can say that pesticides are adequately safe, and we go through
a stringent process to assess them, but we cannot guarantee that
they are safe. We have to keep the situation under review all
the time, in case new evidence comes to light that suggests our
previous decisions were wrong. In terms of how you improve operator
safety, it is a bit like safety on the roads. On the one end of
things you can improve the engineering, the design of roads and
cars, to make them more crashworthy and less dangerous to pedestrians;
and you can also try to train people to be better drivers. You
have to look and see where the most gains can be made. The evidence
we have at the moment is that in this country, compared to what
we had in the past and compared with what we have in many other
parts of the developing world in particular, the handling of portfolio
pesticides on farms is pretty good; but that is not to say it
could not be better. We are always looking for ways of improving
it, and engineering controls have the advantage that they do not
rely on somebody's effort to make them work. If you can have a
system for diluting pesticides that does not involve an individual
coming into contact with a concentrate, which is a major determinant
of individual exposure, that is an advantage, and it is better
than relying on good behaviour by the worker. We are all the time
looking for ways of improving things.
Q312 Mr Wiggin: Obviously, one of the
motivators behind the Voluntary Initiative was a tax, and, going
back to your analogy, increasing road tax does not make people
drive better.
Professor Coggon: It might make
them drive less—a few people! I am not an economist either.
Q313 Chairman: I will attempt to conclude
our proceedings by asking you about Economic Directive 91/414,
which I am sure you are entirely familiar with.
Professor Coggon: Every word of
it!
Q314 Chairman: Some of our Committee
colleagues recently visited Brussels and heard that a negotiation
on a major revision of this Directive is to begin later this year.
Clearly, that is a matter of interest to all of us because it
could result in the most toxic of pesticides being banned. Is
that the conclusion that you might draw from the likely direction
of a revision?
Professor Coggon: I cannot answer
with authority because I do not know what the direction of the
revision is. What I will say is that there have been some pressures
from some countries in Europe to regulate on the hazard associated
with pesticides, in other words the potential for them to cause
damage. That has the advantage of simplicity. You can classify
a chemical according to its hazard, saying this one is much more
toxic weight for weight than another, and therefore we will regulate
it more strictly. However, at the end of the day what really matters
is the risk to the person, and the risk depends not only on the
intrinsic hazard of the material, but on the way in which it is
being handled and the amount to which people get exposed. There
is the possibility if you start regulating on hazard that you
will end up in a paradoxical situation where something gets replaced
by another material which, although less hazardous, because of
the way in which it is used poses a greater risk. It is not a
simple situation and there has to be a lot of careful thought
about the best way forward.
Q315 Chairman: What you have said are
the reasons why what we might deem the more toxic of the pesticides
are currently not banned. That is the logic, because you take
it in the round.
Professor Coggon: Yes, because
in the regulatory process we carry out a risk assessment; we do
not just regulate on the basis of hazard. We first have to identify
the potential adverse effects, and what the relationship is of
those adverse effects to levels of exposure. That comes largely
from animal experiments initially, although it may come from human
data as well once a pesticide has been in use. We then have to
look at how much people might get exposed, given the way in which
the pesticide is going to be used, and decide whether the levels
of exposure will be acceptable, given what we know about its toxicity.
Q316 Chairman: Professor Forman, do you
want to add anything at all?
Professor Forman: On the EC Directive,
absolutely not!
Chairman: I meant in general. I was concerned
that we have left you out of this discussion for the last few
moments. Thank you both very much indeed for what you have said
this afternoon and for being willing to answer our questions.
As usual, if there is anything you wish to add on reflection,
please contact us in the usual way, or if there is anything you
want to amend or correct once you have left this room, we will
be glad to hear from you.
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