Report from the Sub-comittee on the environment and health

Tropospheric ozone
Veterinary drugs and
growth promoters
138
a number of o<strong>the</strong>r, persistent organic contaminants. With frequent
application of sludge on <strong>the</strong> same area, <strong>the</strong> total quantity of xenobiotic
substances can be of <strong>the</strong> same order of magnitude as <strong>the</strong> pesticide load.
Most of <strong>the</strong> xenobiotic organic substances that are supplied to cultivated
land are degradable, but as a rule over a very long period of time. The
presence of xenobiotic substances is undesirable, so for precautionary
reasons, consumption and dispersal are limited as much as possible or, in
<strong>the</strong> case of persistent organic substances, for example, a ban is
introduced. The exposure of <strong>the</strong> agricultural sector to xenobiotic
substances is low compared with o<strong>the</strong>r sectors. Compared with <strong>the</strong> effect
of pesticides, <strong>the</strong> direct effect of xenobiotic substances on cultivated soil
and thus on crops is small. However, relatively little is known about
potential, indirect pollution by xenobiotic substances, for example via air
or through accidental loss, spillage or discharge to water. There may
<strong>the</strong>refore be grounds for concern since <strong>the</strong> long-term effects of even
small concentrations are not known. The aim of environment policy in
this area is a reduction at source, both nationally and internationally, but
in view of <strong>the</strong> continuing supply, <strong>the</strong> load <strong>from</strong> xenobiotic substances
must be monitored on a long-term basis.
The formation of tropospheric ozone is closely linked with nitrogen
oxide pollution <strong>from</strong> traffic, industry and energy production.
Tropospheric ozone must not be confused with <strong>the</strong> ozone in <strong>the</strong>
stratosphere, which is beneficial because it provides protection against
UV radiation. Ozone is formed by <strong>the</strong> action of sunlight on nitrogen
oxides and organic compounds – especially hydrocarbons. Ozone is a
constituent of smog and affects <strong>the</strong> eyes, throat and lungs. It is
particularly harmful to asthmatics. Ozone has a harmful effect on
vegetation when it penetrates <strong>the</strong> plant cells. The damage occurs
especially when <strong>the</strong> concentration of ozone in <strong>the</strong> air is over 40 ppb. The
most serious effect of ozone, both ecologically and economically, is <strong>the</strong>
effect on plant growth and seeding.
Seen in relation to pesticides, ozone is an example of a component of air
pollution that is formed <strong>from</strong> emissions <strong>from</strong> traffic, energy production
and industry and that causes considerable losses to <strong>the</strong> agricultural sector
in <strong>the</strong> form of reduced yields. Work is going on within both <strong>the</strong> EU and
UN-ECE FN-ECE to reduce <strong>the</strong> formation of ozone.
In animal husbandry, regular use is made of a number of veterinary
drugs. Besides drugs for treatment of diseases, large quantities of
prophylactic drugs are used, including <strong>the</strong> so-called growth promoters.
Growth promoters are usually antibiotics but can also be salts of copper
or zinc. Owing to <strong>the</strong> suspicion that use of certain pharmaceuticals can
lead to <strong>the</strong> development of resistant bacteria, attention has recently
focused on farmers’ use of antibiotics. The substances can also be spread
in <strong>the</strong> environment with manure. Since <strong>the</strong> substances in question can be
both biologically active in low concentrations, persistent and mobile in
soil, <strong>the</strong> possibility cannot be excluded that some of <strong>the</strong> veterinary
pharmaceuticals can constitute a risk to <strong>the</strong> environment in line with
many o<strong>the</strong>r xenobiotic substances. Studies have been initiated under <strong>the</strong>
Danish Environmental Research Programme to throw light on <strong>the</strong>se
questions. It will be some years before <strong>the</strong> final results can be expected,