biocide

biocide is a chemical substance capable of killing living organisms, usually in a selective way. Biocides are commonly used in medicine, agriculture, forestry, and in industry where they prevent the fouling of water and oil pipelines. Some substances used as biocides are also employed as anti-fouling agents or disinfectants under other circumstances: chlorine, for example, is used as a short-life biocide in industrial water treatment but as a disinfectant in swimming pools. Many biocides are synthetic, but a class of natural biocides, derived from e.g. bacteria and plants[1], includes brassica oleracea, brassica oleracea gemmifera, and clostridium botulinum bacteria.[citation needed][clarification needed]

A biocide can be:

A pesticide: this includes fungicides, herbicides, insecticides, algicides, molluscicides, miticides and rodenticides.
An antimicrobial: this includes germicides, antibiotics, antibacterials, antivirals, antifungals, antiprotozoals and antiparasites. See also spermicide.

Uses
Biocides can be added to other materials (typically liquids) to protect them against biological infestation and growth. For example, certain types of quaternary ammonium compounds (quats) are added to pool water or industrial water systems to act as an algicide, protecting the water from infestation and growth of algae. Chlorine is also added during wastewater treatment to kill micro-organisms, algae, and so on. It is often impractical to store and use poisonous chlorine gas for water treatment, so alternative methods of adding chlorine are used. These include hypochlorite solutions, which gradually release chlorine into the water, and compounds like sodium dichloro-s-triazinetrione (dihydrate or anhydrous), sometimes referred to as "dichlor", and trichloro-s-triazinetrione, sometimes referred to as "trichlor". These compounds are stable while solid and may be used in powdered, granular, or tablet form. When added in small amounts to pool water or industrial water systems, the chlorine atoms hydrolyze from the rest of the molecule forming hypochlorous acid (HOCl) which acts as a general biocide killing germs, micro-organisms, algae, and so on. Halogenated hydantoin compounds are also used as biocides.


Hazards and environmental risks
Because biocides are intended to kill living organisms, many biocidal products pose significant risk to human health and welfare. Great care is required when handling biocides and appropriate protective clothing and equipment should be used. The use of biocides can also have significant adverse effects on the natural environment. Anti-fouling paints, especially those utilising organic tin compounds such as TBT, have been shown to have severe and long-lasting impacts on marine eco-systems and such materials are now banned in many countries for commercial and recreational vessels (though sometimes still used for naval vessels).

Disposal of used or unwanted biocides must be undertaken carefully to avoid serious and potentially long-lasting damage to the environment.


Classification

European Community Classification
The Biocidal Products Directive 98/8/EC (BPD), the classification of biocides, is broken down into 23 product types (i.e. application categories), with several comprising multiple subgroups:[2]

MAIN GROUP 1: Disinfectants and general biocidal products

Product-type 1: Human hygiene biocidal products
Product-type 2: Private area and public health area disinfectants and other biocidal products
Product-type 3: Veterinary hygiene biocidal products
Product-type 4: Food and feed area disinfectants
Product-type 5: Drinking water disinfectants
MAIN GROUP 2: Preservatives

Product-type 6: In-can preservatives
Product-type 7: Film preservatives
Product-type 8: Wood preservatives
Product-type 9: Fibre, leather, rubber and polymerised materials preservatives
Product-type 10: Masonry preservatives
Product-type 11: Preservatives for liquid-cooling and processing systems
Product-type 12: Slimicides
Product-type 13: Metalworking-fluid preservatives
MAIN GROUP 3: Pest control

Product-type 14: Rodenticides
Product-type 15: Avicides
Product-type 16: Molluscicides
Product-type 17: Piscicides
Product-type 18: Insecticides, acaricides and products to control other arthropods
Product-type 19: Repellents and attractants
MAIN GROUP 4: Other biocidal products

Product-type 20: Preservatives for food or feedstocks
Product-type 21: Antifouling products
Product-type 22: Embalming and taxidermist fluids
Product-type 23: Control of other vertebrates

References
^ Natural biocide-term
^ Directive 98/8/EC of the European Parliament and of the Council of 16 February 1998 concerning the placing of biocidal products on the market

Literature
Wilfried Paulus: Directory of Microbicides for the Protection of Materials and Processes. Springer Netherland, Berlin 2006, ISBN 1-4020-4861-0.
Danish EPA (2001): Inventory of Biocides used in Denmark

See also
Non-pesticide management
Ecological pesticides