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=Drug Residues=
=Drug Residues=
This category consists of:
This category consists of:
# Veterinary Medicines.<br>Veterinary Medicines, after being administered to an animal, will still be present in the animal's tissues (or food products) for a variable ammount of time depending on the drug & the species amongst other things. Drugs given to treat animals intended for food production, if licienced, will have a minimum withdrawal period which must be observed before the animal can go for slaughter (for meat withdrawal). Withdrawal periods also exist for other animal products, e.g. egg withdrawal, milk withdrawal, etc...This is to allow enough time for the drug to be excreted or metabolised sufficiently so that no drug or only insignificant ammounts will be present in any food derived from that animal.<br> If a Veterinary Medicine is not Licienced for use in a particular species for treating a particular condition then (having observed the [[Cascade System]]) the standard withdrawal period of 7 days for meat & 28 days for milk should be observed. Some drugs are specifically prohibited from use in all food animals (e.g. Phenylbutazone, Lignocaine to name two) and some drugs are prohibited in specific types of food producing animal (e.g. Tilmicosin is prohibited in Dairy cows but not beef cows).<br>Veterianry Medicines whose use are widespread in food producing animals are Antimicrobial & Antiparasitic drugs. Residues of ranquilizers are also of concern.<br>Organic producers ofen have to observe much longer withdrawal periods and can only administer drugs when the use has been specifically approved by a vet. Use of drugs other than to treat sick animals is generally not approved (although welfare should not be compromised).<br><br>
# '''Veterinary Medicines.'''<br>Veterinary Medicines, after being administered to an animal, will still be present in the animal's tissues (or food products) for a variable ammount of time depending on the drug & the species amongst other things. Drugs given to treat animals intended for food production, if licienced, will have a minimum withdrawal period which must be observed before the animal can go for slaughter (for meat withdrawal). Withdrawal periods also exist for other animal products, e.g. egg withdrawal, milk withdrawal, etc...This is to allow enough time for the drug to be excreted or metabolised sufficiently so that no drug or only insignificant ammounts will be present in any food derived from that animal.<br> If a Veterinary Medicine is not Licienced for use in a particular species for treating a particular condition then (having observed the [[Cascade System]]) the standard withdrawal period of 7 days for meat & 28 days for milk should be observed. Some drugs are specifically prohibited from use in all food animals (e.g. Phenylbutazone, Lignocaine to name two) and some drugs are prohibited in specific types of food producing animal (e.g. Tilmicosin is prohibited in Dairy cows but not beef cows).<br>Veterianry Medicines whose use are widespread in food producing animals are Antimicrobial & Antiparasitic drugs. Residues of ranquilizers are also of concern.<br>Organic producers ofen have to observe much longer withdrawal periods and can only administer drugs when the use has been specifically approved by a vet. Use of drugs other than to treat sick animals is generally not approved (although welfare should not be compromised).<br><br>
# Agricultural Chemicals..<br>As the use of these substances is generally intentional they can be applied well in advance of harvesting in a controlled manner (this is the case for herbicides, fungicides, fertilizers & rodenticides), thus limiting their presence in feeds then given to animals. Some insecticides may be used nearer to harvest or on animals & their environments.
# '''Agricultural Chemicals.'''<br>As the use of these substances is generally intentional they can be applied well in advance of harvesting in a controlled manner (this is the case for herbicides, fungicides, fertilizers & rodenticides), thus limiting their presence in feeds then given to animals. Some insecticides may be used nearer to harvest or on animals & their environments.
##Insecticides-As the most widely used agricultural chemicals represent the greatest risk to food contamination of this category. Some are extremely environmentally stable & toxic.
##'''''Insecticides'''''-As the most widely used agricultural chemicals represent the greatest risk to food contamination of this category. Some are extremely environmentally stable & toxic.
###Chlorinated Hydrocarbons<br>DDT (Dichloro-Diphenyl-Trichloroethane) is th most well known. It is very durable, accumulates in tissues & persists in the environment. Chlorinated Hydrocarbons are CNS stimulants & cause congestion of internal organs & focal centrilobular necrosis of the liver.
###Chlorinated Hydrocarbons<br>DDT (Dichloro-Diphenyl-Trichloroethane) is th most well known. It is very durable, accumulates in tissues & persists in the environment. Chlorinated Hydrocarbons are CNS stimulants & cause congestion of internal organs & focal centrilobular necrosis of the liver.
###Organophosphates<br>The most widely used insecticides, are much less persistant in the environment & body tissues than Chlorinated Hydrocarbons and hence, present less of a risk. They can however, be extremely toxic to mammals causing non-specific acute signs or chronic lung congestion. They may be an Occupational Hazard.
###Organophosphates<br>The most widely used insecticides, are much less persistant in the environment & body tissues than Chlorinated Hydrocarbons and hence, present less of a risk. They can however, be extremely toxic to mammals causing non-specific acute signs or chronic lung congestion. They may be an Occupational Hazard.