environment through removal and subsequent disposal of waste material (including
manure/slurry and “dirty” waters), via excretion of faeces and urine by grazing
animals, through spillage during external application, via wash-off from farmyard
hard surfaces, or by direct exposure/discharge into the environment. For aquacul-
ture treatments, the drug can be added directly to the aquatic environment. Limited
amounts of compound may also be released to the environment from the treatment
of companion animals or the improper disposal of unused products. Each of these
routes of input is described in more detail below.
2.1 Manufacturing
During the manufacture of the active ingredient and formulation of the finished
drug product, raw materials, intermediates or the active substance may be released
into the air, into water in wastewater, and onto the land in the form of solid waste.
The main route of release of both veterinary and human drugs into the environment
during manufacturing is probably via process waste effluents produced during the
cleaning of the active pharmaceutical ingredient and manufacturing equipment
used for coating, blending, tablet compressing and packing (Velagaleti et al.
2002 ). Biological and chemical degradation processes, such as biotransformation,
mineralisation, hydrolysis and photolysis, are thought to remove most drug residues
before process waste effluents or sludge solids are discharged to surface waters/
sewage treatment works or released onto the land (Velagaleti et al. 2002 ). In
addition, a number of practises are often implemented by the industry to reduce
waste generation and material losses. These include process optimisation, produc-
tion scheduling, materials tracking and waste stream segregation (US EPA 1997 ).
Manufacturing plants employ a number of treatment methodologies and technolo-
gies to control and treat emissions and minimise the amount of waste produced.
These include the use of condensers, scrubbers, adsorbent filters and combustion or
incineration for recovery and removal in air emissions. Neutralisation, equalisation,
activated sludge, primary clarification, multimedia filtration, activated carbon,
chemical oxidation and advanced biological processes may be used for treatment
of waste waters (US EPA 1997 ).
2.2 Livestock Treatment
For veterinary products administered either orally or by injection, the major route of
entry of the product into the environment is probably, via excretion following use
and the subsequent disposal of contaminated manure onto land (Metcalfe et al.
2009 ). Many intensively reared farm animals are housed indoors for long periods
at a time. Consequently, large quantities of farmyard manure, slurry or litter are
produced which are then disposed of at high application rates onto the land
(Montforts 1999 ). Although each class of livestock production has different
Veterinary Medicines and the Environment 293