2008-09-19T14:09:36Z

Tkjones: New page: {{unfinished}} {{toplink |linkpage =Principles & Skills For Protecting Public Health|linktext =Principles & Skills For Protecting Public Health |pagetype =VPH |maplink = WikiVPH Content M...

{{unfinished}}

{{toplink
|linkpage =Principles & Skills For Protecting Public Health|linktext =Principles & Skills For Protecting Public Health
|pagetype =VPH
|maplink = WikiVPH Content Map
}}

Introduction to VPH

2008-09-19T14:03:03Z

Tkjones:

{{toplink
|linkpage = Veterinary Public Health|linktext = Veterinary Public Health
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 
What is Veterinary Public Health?

The field of '''Public Health''' concerns the management of human health at the community level. This contrasts to other aspects of medicine where treatment is frequently focussed on the individual. Public Health often involves methods of disease prevention (e.g. vaccination, sanitation, etc.).

Veterinary Public Health concerns all areas of Public Health that can be protected or improved by Veterinary Medicine. See [http://www.who.int/zoonoses/vph/en WHO-VPH]

Under this broad definition Veterinary Public Health could include almost all aspects of veterinary work from treating pets (as this helps people's "..mental & social well-being..") to farm animal veterinary work (as this helps secure food production, essential to public health).

Conventionally Veterinary Public Health as a topic covers the following areas:
=Food production & safety=

It is desirable to consider food production as a chain, with animals reared on the farm (pre-harvest) then going for primary processing (harvest), secondary processing & distribution followed by final preparation (all post-harvest). This "Farm to Fork" concept can be easily described by considering a beef animal on a farm going to slaughter at the abattoir, then the hamburger production plant, then being distributed to a supermarket. The hamburger is then sold, taken home, stored, cooked & eaten.

Veterinary Public Health concerns all aspects of food production chain from controlling epidemic diseases that may impact on agriculture, to ensuring slaughter is conducted safely & humanely, to informing the public on safe ways to store & cook hamburgers.

The safe production of meat is covered in [[Food Safety - WikiVPH| Food Safety]]

=Zoonosis control=
A zoonosis may be defined as any disease and/or infection which is naturally transmissible between animals & man. See [http://www.who.int/zoonoses/en/ WHO-Zoonoses]

They are of major public concern. Headlines on issues like Avian Influenza, BSE (mad cow disease) & Salmonella of eggs have dominated the UK newspaper headlines for the last thirty years.

The picture in developed & developing countries may be quite different as far as zoonoses are concerned. In developed countries the consumer has very little contact with the live animal, limiting transmission from live animals to the general public. In addition food safety is extremely regulated. Despite this food borne disease is still a big problem in developed countries. In the EU in 2006, a total of 175,561 confirmed cases of campylobacteriosis were reported from 21 Member States and reported cases will only represent the tip of the iceberg (see [http://www.efsa.eu.int/EFSA/DocumentSet/Zoon_report_2006_summary_en.pdf?ssbinary=true - The EFSA Journal (2007) 130-Main conclusions on the Community Summary Report on Zoonoses 2006]).

Veterinary Public Health concerns the [[Surveillance - Wikivet|Surveillance]] & control of zoonoses at many different levels be it via disease control programmes at farm level or wild animals or in the abattoir.

See the [[Food Safety - WikiVPH| Food Safety]] section & the section [[Non Food derived Zoonoses - WikiVPH|Non Food derived Zoonoses]].

=Environmental contamination=
Environmental pollutants that arise throught the keeping & use of animals may include pollution of the air, land or water. It can arise through animal waste products as well as chemicals that may be used during production (e.g. insecticides, antibiotics, etc...).

In addition practicing vets will also produce potential environmental contaminants in the form of used needles, syringes, animal tissue & other clinical waste.

All of these materials have to be dealt with in a safe & controlled way. See the Section [[Environmental Contamination - Wikivet| Environmental Contamination]].

=The role of animals in society=
This aspect of Veterinary Public Helath deals with a number of ethical issues. Welfare of animals is an ever present issue regardless of the setting, whether it concerns pet animals, production animals or wild animals.

Where the line that defines acceptable & unacceptable welfare conditions lies is different for different individuals from different countries & cultures, however, it is common for minimum welfare standards to be defined in legislation (see [[Legislation-Wikivet|Legislation]]).

Other issues may concern the use of animals in science, not just for experimentation, but the use of transgenic animals (an animals who has had its genome deliberately altered by genetic engineering techniques as opposed to selective breeding) & xenotransplantation (the transplantation of organs or tissues from one species to another) or the emergence of resistance to antimicrobial drugs due to their use in animals (see [[Antimicrobial Resistance - Wikivet| Antimicrobial Resistance]]).

Food Derived Hazards to Human Health

2008-09-19T11:17:48Z

Tkjones:

{{unfinished}}

{{toplink
|linkpage = Food Safety - WikiVPH|linktext = Food Safety
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 

A [[hazard - WikiVPH|Hazard]] is something that is potentially harmful - to humans, animals or the environment. There are many different hazards to humans that can arise in food. This section will describe the main ones.

They are:
=Foreign Bodies=

Foreign body contamination is the main cause of customer complaints & litergation relating to food hazards in the UK & other develooped countries. The foreign bodies may be metal, stone, plastic, hair etc.... Cereals, bread & flour are most commonly affected followed by processed meats, poultry & fish. Deteection systems may be in place. They may consist of metal detectors, X-ray machines or just visual inspection (1).

=Pathogenic Organisms & their Toxins=

Most overt food borne disease is caused by this category of hazards. Consequently this section will be dealt with in depth, see [[Foodborne Pathogenic Organisms - WikiVPH|Foodborne Pathogenic Organisms]].

=Chemical Hazards=
See [[Chemical Hazards - WikiVPH|Chemical Hazards]]

=Radionucleotides=
Although unusual, contamination of livestock with caesium-137 occurred after the Chernobyl nuclear power plant disaster in 1986.

=Genetically Modified (GM) Foods=
In this context this refers to organisms who have have had their genetic make up altered by molecular bioengineering. This can bring about transgenic organisms that carry genes taken from different species.

Arguments against GM foods is that a GM strain may be used to such an extent that it limits biological diversity, causing a loss of the genetic material contained in lost & unused non-GM organisms, potentially compromising food security. Furthermore, if the GM strains are provided by a few multinational companies it could lead to an undesirable dependancy on these companies. Other issues are potential antimicrobial resistance arising through certain manufacturing conditions used in the creation some GM organisms. Also concern exists about the development of resistance to insecticides & herbicides produced by some GM organisms.

Countering this, the use of GM foods could lead to increased production & reduced costs along with better [[organoleptic]] properties.

The risk posed by GM foods is difficult to assess due to a lack of knowledge about their use & consequences. Regardless customers want to know if their food contains GM products or not. Differences in attitudes towards GM foods in the USA & the EU have led to trade wars.

The use of GM organisms is more accepted in medical biotechnology than food production.

See [http://www.efsa.europa.eu/EFSA/KeyTopics/efsa_locale-1178620753812_GMO.htm| EFSA-Genetically Modified Organisms]

=[[References - WikiVPH|References]]=

Food Derived Hazards to Human Health

2008-09-19T11:15:10Z

Tkjones:

{{toplink
|linkpage = Food Safety - WikiVPH|linktext = Food Safety
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 

A [[hazard - WikiVPH|Hazard]] is something that is potentially harmful - to humans, animals or the environment. There are many different hazards to humans that can arise in food. This section will describe the main ones.

They are:
=Foreign Bodies=

Foreign body contamination is the main cause of customer complaints & litergation relating to food hazards in the UK & other develooped countries. The foreign bodies may be metal, stone, plastic, hair etc.... Cereals, bread & flour are most commonly affected followed by processed meats, poultry & fish. Deteection systems may be in place. They may consist of metal detectors, X-ray machines or just visual inspection (1).

=Pathogenic Organisms & their Toxins=

Most overt food borne disease is caused by this category of hazards. Consequently this section will be dealt with in depth, see [[Foodborne Pathogenic Organisms - WikiVPH|Foodborne Pathogenic Organisms]].

=Chemical Hazards=
See [[Chemical Hazards - WikiVPH|Chemical Hazards]]

=Radionucleotides=
Although unusual, contamination of livestock with caesium-137 occurred after the Chernobyl nuclear power plant disaster in 1986.

=Genetically Modified (GM) Foods=
In this context this refers to organisms who have have had their genetic make up altered by molecular bioengineering. This can bring about transgenic organisms that carry genes taken from different species.

Arguments against GM foods is that a GM strain may be used to such an extent that it limits biological diversity, causing a loss of the genetic material contained in lost & unused non-GM organisms, potentially compromising food security. Furthermore, if the GM strains are provided by a few multinational companies it could lead to an undesirable dependancy on these companies. Other issues are potential antimicrobial resistance arising through certain manufacturing conditions used in the creation some GM organisms. Also concern exists about the development of resistance to insecticides & herbicides produced by some GM organisms.

Countering this, the use of GM foods could lead to increased production & reduced costs along with better [[organoleptic]] properties.

The risk posed by GM foods is difficult to assess due to a lack of knowledge about their use & consequences. Regardless customers want to know if their food contains GM products or not. Differences in attitudes towards GM foods in the USA & the EU have led to trade wars.

The use of GM organisms is more accepted in medical biotechnology than food production.

See [http://www.efsa.europa.eu/EFSA/KeyTopics/efsa_locale-1178620753812_GMO.htm| EFSA-Genetically Modified Organisms]

=[[References - WikiVPH|References]]=

Food Derived Hazards to Human Health

2008-09-18T18:05:28Z

Tkjones: /* Genetically Modified (GM) Foods */

Food Derived Hazards to Human Health

2008-09-18T18:05:12Z

Tkjones: /* Genetically Modified (GM) Foods */

{{unfinished}}

{{toplink
|linkpage = Food Safety - WikiVPH|linktext = Food Safety
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 

A [[hazard - WikiVPH|Hazard]] is something that is potentially harmful - to humans, animals or the environment. There are many different hazards to humans that can arise in food. This section will describe the main ones.

They are:
=Foreign Bodies=

Foreign body contamination is the main cause of customer complaints & litergation relating to food hazards in the UK & other develooped countries. The foreign bodies may be metal, stone, plastic, hair etc.... Cereals, bread & flour are most commonly affected followed by processed meats, poultry & fish. Deteection systems may be in place. They may consist of metal detectors, X-ray machines or just visual inspection (1).

=Pathogenic Organisms & their Toxins=

Most overt food borne disease is caused by this category of hazards. Consequently this section will be dealt with in depth, see [[Foodborne Pathogenic Organisms - WikiVPH|Foodborne Pathogenic Organisms]].

=Chemical Hazards=
See [[Chemical Hazards - WikiVPH|Chemical Hazards]]

=Radionucleotides=
Although unusual, contamination of livestock with caesium-137 occurred after the Chernobyl nuclear power plant disaster in 1986.

=Genetically Modified (GM) Foods=
In this context this refers to organisms who have have had their genetic make up altered by molecular bioengineering. This can bring about transgenic organisms that carry genes taken from different species.

Arguments against GM foods is that a GM strain may be used to such an extent that it limits biological diversity, causing a loss of the genetic material contained in lost & unused non-GM organisms, potentially compromising food security. Furthermore, if the GM strains are provided by a few multinational companies it could lead to an undesirable dependancy on these companies. Other issues are potential antimicrobial resistance arising through certain manufacturing conditions used in the creation some GM organisms. Also concern exists about the development of resistance to insecticides & herbicides produced by some GM organisms.

Countering this, the use of GM foods could lead to increased production & reduced costs along with better [[organoleptic]] properties.

The risk posed by GM foods is difficult to assess due to a lack of knowledge about their use & consequences. Regardless customers want to know if their food contains GM products or not. Differences in attitudes towards GM foods in the USA & the EU have led to trade wars.

The use of GM organisms is more accepted in medical biotechnology than food production.

See [http://www.efsa.europa.eu/EFSA/KeyTopics/efsa_locale-1178620753812_GMO.htm|EFSA-Genetically Modified Organisms]

=[[References - WikiVPH|References]]=

Food Derived Hazards to Human Health

2008-09-18T18:02:11Z

Tkjones: /* Genetically Modified (GM) Foods */

Food Derived Hazards to Human Health

2008-09-18T17:50:23Z

Tkjones: /* Genetically Modified (GM) Foods */

{{unfinished}}

{{toplink
|linkpage = Food Safety - WikiVPH|linktext = Food Safety
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 

A [[hazard - WikiVPH|Hazard]] is something that is potentially harmful - to humans, animals or the environment. There are many different hazards to humans that can arise in food. This section will describe the main ones.

They are:
=Foreign Bodies=

Foreign body contamination is the main cause of customer complaints & litergation relating to food hazards in the UK & other develooped countries. The foreign bodies may be metal, stone, plastic, hair etc.... Cereals, bread & flour are most commonly affected followed by processed meats, poultry & fish. Deteection systems may be in place. They may consist of metal detectors, X-ray machines or just visual inspection (1).

=Pathogenic Organisms & their Toxins=

Most overt food borne disease is caused by this category of hazards. Consequently this section will be dealt with in depth, see [[Foodborne Pathogenic Organisms - WikiVPH|Foodborne Pathogenic Organisms]].

=Chemical Hazards=
See [[Chemical Hazards - WikiVPH|Chemical Hazards]]

=Radionucleotides=
Although unusual, contamination of livestock with caesium-137 occurred after the Chernobyl nuclear power plant disaster in 1986.

=Genetically Modified (GM) Foods=
In this context this refers to organisms who have have had their genetic make up altered by molecular bioengineering. This can bring about transgenic organisms that carry genes taken from different species.

Arguments against GM foods is that a GM strain may be used to such an extent that it limits biological diversity, causing a loss of the genetic material contained in lost & unused non-GM organisms, potentially compromising food security. Furthermore, if the GM strains are provided by a few multinational companies it could lead to an undesirable dependancy on these companies. Other issues are potential antimicrobial resistance arising through certain manufacturing conditions used in the creation some GM organisms. Also concern exists about the development of resistance to insecticides & herbicides produced by some GM organisms.

Countering this, the use of GM foods could lead to increased production & reduced costs along with better [[organoleptic]] properties.

The use of GM organisms is more accepted in medical biotechnology than food production.

=[[References - WikiVPH|References]]=

Food Derived Hazards to Human Health

2008-09-18T17:45:22Z

Tkjones: /* Genetically Modified Foods */

2008-09-18T16:47:09Z

Tkjones: /* Drug Residues */

{{unfinished}}

{{toplink
|linkpage = Food Derived Hazards to Human Health - WikiVPH|linktext = Food Derived Hazards to Human Health
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 
Chemical contamination of foodstuffs can be due to their presence in the environment, or their intentional or unintentional application somewhere along the food chain. Some chemical toxins may occur naturally. Controlling chemicals which are only unintentionally present in the food chain is obviously difficult.
Foodborne Chemical Hazards may be from the following categories:
=Drug Residues=
This category consists of:
# '''Veterinary Medicines.''' 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. 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). Veterianry Medicines whose use are widespread in food producing animals are Antimicrobial & Antiparasitic drugs. Residues of ranquilizers are also of concern. 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). 
# '''Agricultural Chemicals.''' 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.
###''Chlorinated Hydrocarbons'' 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'' 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.
##'''''Herbicides'''''-Are not usually used on animal food crops but may sometimes be used for plants used for animal bedding causing residue problems. Some may contain [[Dioxins]].
##'''''Fungicides'''''-(e.g. dicloran & folpet) Do not usually cause residue problems. They may contain heavy metals. They are often dyed to allow identification of treated crops, however, accidental feeding of treated crops to animals or use in cereal foods has led to poisonings.
##'''''Fertilizers'''''-Can cause significant environmental problems, particularly if they contaminate run-off waters. Algal blooms may result aswell as the growth of toxic algae that may contaminate shellfish.
##'''''Rodenticides'''''- (e.g. Warfarin & Antu) although widely used should not contaminate foodstuffs. 
#'''Growth Promoters''' Growth Promoters are used amongst other things to increase production performance of animals and not for a health benefit to the animal or consumer. Commonly used Growth Promoters are Hormone-like compounds & antimicrobials. Growth Promoters Growth Promoters are not allowed in the EU but are in the USA & other countries. This has important trade implications.
##'''''Hormone-like growth promoters''''' These include synthetic hormones (e.g.Diethylsibestrol), natural hormones (e.g. estradiol, Progesterone, Testosterone), fungal oestrogens (Zearalenone), Beta-agonists (Trenbolone) and thyreostatics. Risk associated with these compunds can be difficult to evaluate as administered natural hormones may be dificult to distinguish from endogenous hormones in animals & people. Also synthetic hormones given to young animals may not be detectable at time of slaughter.
##'''''Antimicrobial Growth Promoters''''' Fed are low but continuous doses in feed they have been observed to cause increased growth rates. Although not understood the mechanism of action could be via suppressing disadvantagous intestinal microflora or direct anabolic effects of the drugs themselves. Virginamycin, bacitracin, polymyxin B & sulphonamides are commonly used. There used is strongly suspected of causing [[Antimicrobial Resistance - WikiVPH|Antimicrobial Resistance]].
=References= See [[References - WikiVPH|References]]

=Environmental Chemical Hazards=
Often from an industrial source they include:
#'''Heavy Metals''' (e.g. Lead, Arsenic, Mercury, Cadmium, Fluorine &Selenium)
##'''''Lead'''''-Lead can occur in animals grazing near smelting plants or from animals licking lead based paints or old car batteries. Lead then accumulates in the bones. Acute poisoning may result in high levels in the liver & kidneys. Chronic exposure may cause softening & cavitation of the CNS.
##'''''Arsenic'''''-Contamination of food animals with arsenic is typically due to exposure to arsenical herbicides, rodenticides or insecticides. Its accumulation in the liver & kidneys can lead to fatty degeneration. It also accumulates in the bones.
##'''''Mercury'''''-Rare cases of mercury poisoning have been due to animals being fed with grain treated with mercury-based anti-fungicides. The result is enlarged internal organs & petechiation). Inorganic mercury is also stored in the liver & kidneys, whereas organic mercury is more widely distributed. See [http://www.env.go.jp/en/chemi/hs/minamata2002/| Minamata disease]
##'''''Cadmium'''''-An increasing problem, high cadmium levels occur in animals grazing pasture irregated with aerobically digested sludge. Contamination of shell fish & fish also occur as cadmium may contaminate water. It accumulates in the bidy tissues & may cause kidney failure. Prolonged accumulation is required to reach toxic levels.

=Food Additives=
This refers to chemicals deliberately added to foods in a controlled manor & at a level that is judged as posing no significant health risk. However, uncertain circulmstances some food additives may present a health risk. They may be curing agents, smoke compunds, antioxidants, preservatives or agents improve sensory qualities.

#'''Additives to improve Sensory Qualities''' There are many food additives for food that do not offer any food safety benefits & are added to improve the sensory qualities (Organoleptic qualities) of the food. Possible health risks of these additives are poorly defined but some associations have been put forward (e.g. hyperactivity in children). Organoleptic qualities that they may afffect are colour (e.g. dyes), emulsifiers, sweetners (e.g. saccharin, acesulfame k, aspartame) & flavour enhancers (e.g. Sodium Glutamate).
#'''Nitrites & Nitrates''' Nitrogen Dioxide reacts with myoglobin in meat to give it an attractive, bright red colour. Nitrates helps to inhibit the growth of clostridial spores in cured meats (e.g. sausages) & provide the cured flavour. Nitrites are toxic if concentrations are too high (so levels are monitored), it may combine with the blood pigment Haemoglobin to form nitrosohaemoglobin. In addition, the nitrites may react with amines in the meat to form Nitrosamine compounds that are carcinogenic. This small risk is seen to be outweighed by that health benefits of inhibiting ''C.botulinum''. Nitrites levels of tobacco smoke & some vegetables (e.g. spinach) are many times higher than in cured meats. See [[Preservation Methods - WikiVPH|Presevation Methods]].
#'''Polyphosphates''' Polyphosphates are added to meats to increase the meat proteins ability to bind water. This improves texture & increases the weight of the meat. THey could potentially cause a disturbance to the bodies calcium/phosphorus balance due to excess phosphorous intake. Children would be particuarly affected by this due to their rapid bone growth.
#'''Smoke''' Smoke flavours are used to improve the organoleptic properties of some foods. Some compounds from smoke have antimicrobial properties (e.g.organic acids & phenols) and some smoke compounds are carcinogenic. Polycyclic aromatic hydrocarbons, such as 3,4 benzpyrene, are carcinogens produced when smoking at over 300◦C. A liquid smoke product is frequently used that has the toxic compunds removed but retains the compounds that improve organoleptic qualities.
#'''Plastic Packaging Compounds''' Vinyl chloride monomers, that are carcinogenic, are used to produce Polyvinyl Chloride (PVC) plastic packages, that are safe/non-carcinogenic. However, in some circumstances the toxic monomers may still be present & could potentially transfer to the food. Other plastics, not intended for microwave use, if microwaved may react with fats in the food to produce toxic substances.

=Mycotoxins=
Some fungi produce toxins (Mycotoxins). If they grow in animal feeds any toxins then consumed may be present in products that come from these animals. Toxin producing fungi can also grow on some foods after harvest. Mycotoxins of concern are Aflatoxins produced by ''Aspergillus flavus'' & ''A. parasiticus''. They are carcinogenic, affecting the liver. Ochratoxins produced by ''Penecillium spp.'' & some ''Aspergillus'' moulds and associated with pigs, affect the kidney.

=Marine Toxins=
Algae can produce toxins that may then accumulate in filter-feeding shellfish. Use of Phosphate-based fertilizers on farms may lead to algal blooms in costal waters (which may be seen as a red tide) leading to toxin production. These toxins may cause Paralytic Shellfish Poisoning (PSP) & other similar poisonings. Algal toxins are not destroyed by cooking. The clinical signs of PSP are numbness & tingling of the mouth & lips. Cranial nerves may be affected. Weakness of the limbs & paralysis progress & in some cases death may occur due respiratory failure due to paralysis of the respiratory muscles.

=Plant Toxins=
=Toxic Amines=

Chemical Hazards

2008-09-18T16:44:40Z

Tkjones: /* Marine Toxins */

Chemical Hazards

2008-09-18T16:29:52Z

Tkjones: /* Marine Toxins */

{{unfinished}}

{{toplink
|linkpage = Food Derived Hazards to Human Health - WikiVPH|linktext = Food Derived Hazards to Human Health
|pagetype = VPH
|maplink = WikiVPH Content Map
}}
 
Chemical contamination of foodstuffs can be due to their presence in the environment, or their intentional or unintentional application somewhere along the food chain. Some chemical toxins may occur naturally. Controlling chemicals which are only unintentionally present in the food chain is obviously difficult.
Foodborne Chemical Hazards may be from the following categories:
=Drug Residues=
This category consists of:
# '''Veterinary Medicines.''' 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. 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). Veterianry Medicines whose use are widespread in food producing animals are Antimicrobial & Antiparasitic drugs. Residues of ranquilizers are also of concern. 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). 
# '''Agricultural Chemicals.''' 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.
###''Chlorinated Hydrocarbons'' 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'' 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.
##'''''Herbicides'''''-Are not usually used on animal food crops but may sometimes be used for plants used for animal bedding causing residue problems. Some may contain [[Dioxins]].
##'''''Fungicides'''''-(e.g. dicloran & folpet) Do not usually cause residue problems. They may contain heavy metals. They are often dyed to allow identification of treated crops, however, accidental feeding of treated crops to animals or use in cereal foods has led to poisonings.
##'''''Fertilizers'''''-Can cause significant environmental problems, particularly if they contaminate run-off waters. Algal blooms may result aswell as the growth of toxic algae that may contaminate shellfish.
##'''''Rodenticides'''''- (e.g. Warfarin & Antu) although widely used should not contaminate foodstuffs. 
#'''Growth Promoters''' Growth Promoters are used amongst other things to increase production performance of animals and not for a health benefit to the animal or consumer. Commonly used Growth Promoters are Hormone-like compounds & antimicrobials. Growth Promoters Growth Promoters are not allowed in the EU but are in the USA & other countries. This has important trade implications.
##'''''Hormone-like growth promoters''''' These include synthetic hormones (e.g.Diethylsibestrol), natural hormones (e.g. estradiol, Progesterone, Testosterone), fungal oestrogens (Zearalenone), Beta-agonists (Trenbolone) and thyreostatics. Risk associated with these compunds can be difficult to evaluate as administered natural hormones may be dificult to distinguish from endogenous hormones in animals & people. Also synthetic hormones given to young animals may not be detectable at time of slaughter.
##'''''Antimicrobial Growth Promoters''''' Fed are low but continuous doses in feed they have been observed to cause increased growth rates. Although not understood the mechanism of action could be via suppressing disadvantagous intestinal microflora or direct anabolic effects of the drugs themselves. Virginamycin, bacitracin, polymyxin B & sulphonamides are commonly used. There used is strongly suspected of causing [[Antimicrobial Resistance - WikiVPH|Antimicrobial Resistance]].

=Environmental Chemical Hazards=
Often from an industrial source they include:
#'''Heavy Metals''' (e.g. Lead, Arsenic, Mercury, Cadmium, Fluorine &Selenium)
##'''''Lead'''''-Lead can occur in animals grazing near smelting plants or from animals licking lead based paints or old car batteries. Lead then accumulates in the bones. Acute poisoning may result in high levels in the liver & kidneys. Chronic exposure may cause softening & cavitation of the CNS.
##'''''Arsenic'''''-Contamination of food animals with arsenic is typically due to exposure to arsenical herbicides, rodenticides or insecticides. Its accumulation in the liver & kidneys can lead to fatty degeneration. It also accumulates in the bones.
##'''''Mercury'''''-Rare cases of mercury poisoning have been due to animals being fed with grain treated with mercury-based anti-fungicides. The result is enlarged internal organs & petechiation). Inorganic mercury is also stored in the liver & kidneys, whereas organic mercury is more widely distributed. See [http://www.env.go.jp/en/chemi/hs/minamata2002/| Minamata disease]
##'''''Cadmium'''''-An increasing problem, high cadmium levels occur in animals grazing pasture irregated with aerobically digested sludge. Contamination of shell fish & fish also occur as cadmium may contaminate water. It accumulates in the bidy tissues & may cause kidney failure. Prolonged accumulation is required to reach toxic levels.

=Food Additives=
This refers to chemicals deliberately added to foods in a controlled manor & at a level that is judged as posing no significant health risk. However, uncertain circulmstances some food additives may present a health risk. They may be curing agents, smoke compunds, antioxidants, preservatives or agents improve sensory qualities.

#'''Additives to improve Sensory Qualities''' There are many food additives for food that do not offer any food safety benefits & are added to improve the sensory qualities (Organoleptic qualities) of the food. Possible health risks of these additives are poorly defined but some associations have been put forward (e.g. hyperactivity in children). Organoleptic qualities that they may afffect are colour (e.g. dyes), emulsifiers, sweetners (e.g. saccharin, acesulfame k, aspartame) & flavour enhancers (e.g. Sodium Glutamate).
#'''Nitrites & Nitrates''' Nitrogen Dioxide reacts with myoglobin in meat to give it an attractive, bright red colour. Nitrates helps to inhibit the growth of clostridial spores in cured meats (e.g. sausages) & provide the cured flavour. Nitrites are toxic if concentrations are too high (so levels are monitored), it may combine with the blood pigment Haemoglobin to form nitrosohaemoglobin. In addition, the nitrites may react with amines in the meat to form Nitrosamine compounds that are carcinogenic. This small risk is seen to be outweighed by that health benefits of inhibiting ''C.botulinum''. Nitrites levels of tobacco smoke & some vegetables (e.g. spinach) are many times higher than in cured meats. See [[Preservation Methods - WikiVPH|Presevation Methods]].
#'''Polyphosphates''' Polyphosphates are added to meats to increase the meat proteins ability to bind water. This improves texture & increases the weight of the meat. THey could potentially cause a disturbance to the bodies calcium/phosphorus balance due to excess phosphorous intake. Children would be particuarly affected by this due to their rapid bone growth.
#'''Smoke''' Smoke flavours are used to improve the organoleptic properties of some foods. Some compounds from smoke have antimicrobial properties (e.g.organic acids & phenols) and some smoke compounds are carcinogenic. Polycyclic aromatic hydrocarbons, such as 3,4 benzpyrene, are carcinogens produced when smoking at over 300◦C. A liquid smoke product is frequently used that has the toxic compunds removed but retains the compounds that improve organoleptic qualities.
#'''Plastic Packaging Compounds''' Vinyl chloride monomers, that are carcinogenic, are used to produce Polyvinyl Chloride (PVC) plastic packages, that are safe/non-carcinogenic. However, in some circumstances the toxic monomers may still be present & could potentially transfer to the food. Other plastics, not intended for microwave use, if microwaved may react with fats in the food to produce toxic substances.

=Mycotoxins=
Some fungi produce toxins (Mycotoxins). If they grow in animal feeds any toxins then consumed may be present in products that come from these animals. Toxin producing fungi can also grow on some foods after harvest. Mycotoxins of concern are Aflatoxins produced by ''Aspergillus flavus'' & ''A. parasiticus''. They are carcinogenic, affecting the liver. Ochratoxins produced by ''Penecillium spp.'' & some ''Aspergillus'' moulds and associated with pigs, affect the kidney.

=Marine Toxins=
Algae can produce toxins that may then accumulate in filter-feeding shellfish. Use of Phosphate-based fertilizers on farms may lead to algal blooms in costal waters leading to toxin production. These toxins may cause Paralytic Shellfish Poisoning (PSP) & other similar poisonings. Algal toxins are not destroyed by cooking.

=Plant Toxins=
=Toxic Amines=