organic weed management promotes weed suppression, rather than weed elimination, by enhancing crop competition and phytotoxic effects on weeds. Organic farmers integrate cultural, biological, mechanical, physical and chemical tactics to manage weeds without synthetic herbicides.

Organic crop rotations frequently include weed-suppressive cover crops and crops with dissimilar life cycles to discourage weeds associated with a particular crop. Organic farmers strive to increase organic soil matter content, which can support microorganisms that destroy common weed seeds.

Other cultural practices used to enhance crop competitiveness and reduce weed pressure include selection of competitive crop varieties, high-density planting, tight row spacing, and late planting into warm soil to encourage rapid crop germination.

Mechanical and physical weed control practices used on organic farms can be broadly grouped as

• Tillage - turning the soil between crops to incorporate crop residues and soil amendments; remove existing weed growth and prepare a seedbed for planting;
• Cultivation - disturbing the soil after seeding;
• Mowing and cutting - removing top growth of weeds;
• Flame weeding and thermal weeding - using heat to kill weeds; and
• Mulching - blocking weed emergence with organic materials, plastic films, or landscape fabric.

Some naturally-sourced chemicals are allowed for herbicidal use. These include certain formulations of acetic acid (concentrated vinegar), corn gluten meal, and essential oils. A few selective bioherbicides based on fungal pathogens have also been developed. At this time, however, organic herbicides and bioherbicides play a minor role in the organic weed control toolbox.

Weeds can be controlled by grazing. For example, geese have been used successfully to weed a range of organic crops including cotton, strawberries, tobacco, and corn, reviving the practice of keeping cotton patch geese, common in the southern U.S. before the 1950s. Similarly, some rice farmers introduce ducks and fish to wet paddy fields to eat both weeds and insects.

occupational safety and health, see occupational health and safety (OSH)

United States Department of Labor, Occupational Safety and Health Administration.

Safety and Health Topics Pages provide access to selected occupational safety and health information. The subjects of these pages include specific workplace hazards, as well as individual industries. Members of the Editorial Boards evaluate numerous OSHA and non-OSHA references on a given subject to determine which they consider most important in reducing occupational injuries and illnesses. With the continued support of our users, editors, and editorial boards, OSHA's Safety and Health Topics Pages provide assistance for complying with OSHA standards, enabling employers to ensure safer workplaces.

Source: http://www.osha.gov/index.html

the United States Occupational Safety and Health Administration (OSHA) is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970.

Its mission is to prevent work-related injuries, illnesses, and occupational fatality by issuing and enforcing standards for workplace safety and health. The agency is headed by a Deputy Assistant Secretary of Labor.

The OSH Act, which created OSHA also created the National Institute for Occupational Safety and Health (NIOSH) as a research agency focusing on occupational health and safety. NIOSH, however, is not a part of the U.S. Department of Labor.

OSHA federal regulations cover most private sector workplaces. The OSH Act permits states to develop approved plans as long as they cover public sector employees and they provide protection equivalent to that provided under Federal OSHA regulations. In return, a portion of the cost of the approved state program is paid by the federal government.

an oxidizer or an oxidizing agent, also called oxidant, can be defined asa chemical compound that readily transfers oxygen atoms, or a substance that gains electrons in a redox chemical reaction. In both cases, the oxidizing agent becomes reduced in the process.

The dangerous substance definition of an oxidizer is a substance that is not necessarily combustible, but may, generally by yielding oxygen, cause or contribute to the combustion of other material. By this definition some materials that are classified as oxidizing agents by analytical chemists or biochemists are not classified as oxidizing agents in a dangerous materials sense.

Oxidising, literally, means converting to oxide. This process can apply to metals (iron converts to iron oxide), nonmetals (sulfur converts to sulfur oxide), and organic matter (mainly carbon and hydrogen converts to carbon oxide and hydrogen oxide). An obvious oxidizer is oxygen, which forms about 21% of air.

Later, the use of the term expanded to include any time where formal charge is increased (losing electrons), and applies to substances which contain no oxygen (typically halogens and substances rich in these elements, and less commonly sulfur). Oxidising is the opposite of reduction, where formal charge is decreased (gaining electrons). Redox reactions occur when oxidation states of the reactants change. In a redox-system the oxidizing agent is reduced, the reducing agent is oxidized. All atoms in a molecule can be assigned an oxidation number. This number changes when an oxidant acts on a substrate.

Many common oxidizers contain oxygen (KClO₄ is KCl "plus" 2 O₂) and can be considered compact storage of oxygen; a given volume of potassium perchlorate contains much more oxygen than the same volume of air.The most common oxidizers are the following:

Ammonium cerium(IV) nitrate and probably related cerium(IV) compounds
Chlorite, chlorate, perchlorate, and other analogous halogen compounds
Hexavalent chromium compounds such as chromic and dichromic acids and chromium trioxide, pyridinium chlorochromate (PCC), and chromate/dichromate compounds
Hypochlorite and other hypohalite compounds such as bleach
Iodine and other halogens
Nitric acid
Nitrous oxide (N₂O)
Osmium tetroxide (OsO₄)
Ozone
Permanganate salts
Peroxide compounds
Persulfuric acid
Potassium nitrate (KNO₃)
Sulfoxides
Sulfuric acid
Tollens' reagent: ammoniacal silver nitrate

Source: http://en.wikipedia.org/wiki/Oxidizing_agent

a liquid which, while in itself not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material.

oxygen is an element, its atomic number is 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly reactive nonmetallic period 2 element that readily forms compounds (notably oxides) with almost all other elements. At standard temperature and pressure, two atoms of the element bind to O₂ molecule, a colorless, odorless, tasteless gas . Oxygen is the third most abundant element in the universe by mass after hydrogen and helium and the most abundant element by mass in the Earth's crust. Oxygen constitutes 49.2% of the Earth's crust by mass and is the major component of the world's oceans (88.8% by mass). Oxygen gas is the second most common component of the Earth's atmosphere, taking up 21.0% of its volume and 23.1% of its mass (some 10¹⁵ tonnes). Earth is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% O₂ by volume) and Venus have far lower concentrations. However, the O₂ surrounding these other planets is produced solely by ultraviolet radiation impacting oxygen-containing molecules such as carbon dioxide.

All major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that comprise animal shells, teeth, and bone. Oxygen in the form of O₂ is produced from water by cyanobacteria, algae and plants during photosynthesis and is used in cellular respiration for all complex life. Oxygen is toxic to obligately anaerobic organisms, which were the dominant form of early life on Earth until O₂ began to accumulate in the atmosphere 2.5 billion years ago.

Another form of oxygen, ozone (O₃), helps protect the biosphere from ultraviolet radiation with the high-altitude ozone layer, but is a pollutant near the surface where it is a by-product of smog. At even higher low earth orbit altitudes atomic oxygen is a significant presence and a cause of erosion for spacecraft.

The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere. In the present equilibrium, production and consumption occur at the same rate of roughly 1/2000th of the entire atmospheric oxygen per year.

Free oxygen also occurs in solution in the world's water bodies. The increased solubility of O₂ at lower temperatures has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content. Polluted water may have reduced amounts of O₂ in it, depleted by decaying algae and other biomaterials (eutrophication). Scientists assess this aspect of water quality by measuring the water's biochemical oxygen demand, or the amount of O₂ needed to restore it to a normal concentration.

In nature, free oxygen is produced by the light-driven splitting of water during oxygenic photosynthesis. Green algae and cyanobacteria in marine environments provide about 70% of the free oxygen produced on earth and the rest is produced by terrestrial plants.

A simplified overall formula for photosynthesis is:

6 CO₂ + 6 H₂O + photons → C₆H₁₂O₆ + 6 O₂ (or simply carbon dioxide + water + sunlight → glucose + dioxygen)

Photolytic oxygen evolution occurs in the thylakoid membranes of photosynthetic organisms and requires the energy of four photons. Many steps are involved, but the result is the formation of a proton gradient across the thylakoid membrane, which is used to synthesize ATP via photophosphorylation. The O₂ remaining after oxidation of the water molecule is released into the atmosphere.

Molecular dioxygen, O₂, is essential for cellular respiration in all aerobic organisms. Oxygen is used in mitochondria to help generate adenosine triphosphate (ATP) during oxidative phosphorylation. The reaction for aerobic respiration is essentially the reverse of photosynthesis and is simplified as:

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + 2880 kJ·mol^-1

In vertebrates, O₂ is diffused through membranes in the lungs and into red blood cells. Hemoglobin binds O₂, changing its color from bluish red to bright red. Other animals use hemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters). A liter of blood can dissolve 200 cm³ of O₂.

An adult human in rest inhales 1.8 to 2.4 grams of oxygen per minute.This amounts to more than 6 billion tonnes of oxygen inhaled by humanity per year. (Source: Wikipedia)

An aerobic environment is characterized by the presence of free oxygen (O₂) while an anaerobic environment lacks free oxygen but may contain atomic oxygen bound in compounds such as nitrate (NO₃), nitrite (NO₂), and sulfites (SO₃). Aerobe organisms, including microbes require O₂ as their terminal electron acceptor, but anaerobe microbes use a bound form of oxygen instead. There is by definition a byproduct of anaerobic decomposition − the non-oxygen element must go somewhere when the oxygen atom is biochemically removed by the microbe. When sulfites are present, the byproduct is hydrogen sulfide, a foul smell corrosive gas. When nitrites/nitrates are present, the byproduct is inert nitrogen gas.

Most microbes in wastewaters, in deeper waters and soil layers are facultative. That is in the presence of oxygen they act as aerobes, and in the absence of oxygen they act as anaerobes even if bound oxygen is present in large amounts. Aerobic respiration is favored, because the biochemical pathway using O₂ provides a much higher oxidation/reduction potential and is energetically favored.

The free or bound oxygene contentsof the environment can be characterised by the redoxpotential, a measure in volts, which gives the affinity of a substance or an environment for electrons compared with hydrogen, which has a redoxpotential of zero (0).

ethers or alcohols added to gasoline to enhance the octane number and reduce CO production. The most widely used oxygenate is methyl tert-butyl ether (MTBE) produced from methanol and isobutylene. They are water-soluble resulting in fast spreading with groundwater after leaching.

a layer of the atmosphere composed of ozone gas (O₃) that resides approximately 25 miles above the Earth's surface and absorbs solar ultraviolet radiation that can be harmful to living organisms.
 

p-tert-butylphenol is used as an intermediate for phenol resins and polycarbonate resins. It is also used as a raw material for construction elements and floors in buildings.

CAS NO: 98-54-4

Melting Point: 99.3 °C
Boiling Point: 237 °C (at 1,013 hPa)
Density: 0.92 g/m3 at 110 °C
Vapour Pressure: 1.3 x 102 Pa at 60 °C
Partition Coefficient (Log Pow): 3.29 at 25 °C
Water Solubility: 610 mg/l at 25 °C
pKa: 10.16 at 25 °Chttp://enfo.hu/mokka/secure/.tmp/glossary/glossary_edit.php

It is not photodegradable, not ready to hydrolyse, readily biodegradable, bioaccumulated by aquatic ecosystem: 34–120.

The production volume of p-t-butylphenol in Japan is 5,000 tonnes/year in 1993. According to ECDIN database, the production volume of USA is 11,000 tonnes/year in 1993. According to IUCLID database, maximum production volume is 10,000 tonnes/year. Less than 5000 tonnes/year are produced in France. Less than 1000 tonnes/year are sold to be used either as a chemical intermediate for the production of vulcanization agents or as for the production of phenolic resins.

The potential environmental distribution of p-t-butylphenol obtained from a generic fugacity model (Mackey level III) shows that it will be mainly distributed to water. The main route of human exposure is inhalation with a limited numbers of workers potentially exposed during sampling and bag or tank filling operations.

No concentration was measured and no presence of the substance was detected in the environment. Release into environment may happen only from production or transport, because the substance is not used out of the production site. Distribution in the environment when released into air, water and soil can be calculated by transport modelling:
released into air: air: 39.7%; water: 23.3%; soil: 35.9%; sediment: 1.1%;
released into water: air: 0.2%; water: 95.3%; soil: 0.2%; sediment: 4.4%;
release into soil: air: 0.0%; 99.6 %; soi: 0.4%; sediment: 0.0%.

Acute toxicity of p-t-butylphenol is low via any administration routes. This chemical is considered as an irritant to the skin, eyes and respiratory tract. The possibility of skin sensitization in humans still remains because of some positive results in human patch tests, despite negative results in animal experiments (OECD TG 406). The depigmentation was observed on the skin of various animals and humans exposed to this chemical. This change was likely induced by exposure to this chemical not only via direct contact but also via inhalation or ingestion route. In the OECD combined repeat dose and reproductive/developmental screening toxicity test (OECD TG 422) of rats by gavage at doses of 20, 60 and 200 mg/kg/day for 46 days, this chemical showed neither systemic toxicity nor reproductive toxicity even at the highest dose of 200 mg/kg/day. Although a noisy respiratory sound was induced in a few females at 200 mg/kg/day, it was considered due to irritation of the respiratory tract caused by this chemical. In a dose-finding study (14 days), this changed to respiratory difficulty, especially at 1,000 mg/kg/day. In other studies by the longer and higher exposure in diet (approx. 1 g/kg b.w./day, for 20 or 51 weeks), forestomach hyperplasia was induced. This chemical showed clear negative results in gene mutation tests. However, one
chromosomal aberration study indicated structural chromosome aberration and polyploidy with metabolic activation in CHL/IU cells (OECD TG 473) although other studies in rat lymphocytes (OECD TG 473) and in rat liver epithelial-type cells resulted in negative. Therefore, the possibility of in vivo genotoxicity still remains. There was no sufficient carcinogenicity study and no evidence of carcinogenesis in manufacturing workers, however, a two-stage carcinogenicity study indicated this chemical has promoting activity of forestomach carcinogenesis (papilloma and squamous carcinoma) in rats treated with N-methyl-N’-nitro-N-nitrosoguanidine (MNNG). Furthermore, since the structural related chemical, BHA, (2(3)-tert-butyl-methoxylphenol) is a clear carcinogen, a carcinogenic potential of this chemical could not be ruled out. It is a reprotoxic substance.

p-t-Butylphenol is a stable solid and is classified as a readily biodegradable chemical (OECD TG 301). Bioaccumulation factors range from 34-120. The lowest acute and chronic toxicity data were 48h EC50 (3.4 mg/l) of Daphnia magna and 21d NOEC (0.73 mg/l) of Daphnia magna, respectively. An assessment factor of 100 was chosen and applied to the chronic toxicity data (NOEC), because only two NOEC values (algae and Daphnia). PNEC of p-t-butylphenol is 7.3 x 10^-3 mg/l (OECD classification categories for substances hazardous to the aquatic environment; Class: Acute II), p-tbutylphenol may have potential chronic toxicity to aquatic organisms, because NOEC of Daphnia is relatively low and the chemical has moderately bioaccumulative potential.

Personal protection: safety glasses, good ventilation.

Source: http://www.inchem.org/documents/sids/sids/98544.pdf

PAH is an acronym for Poly-Aromatic hydrocarbons (PAH), a chemical compound that contains more than one fused benzene ring. They are commonly found in petroleum fuels, coal products, and tar; e.g. Naphthalene, anthracene, phenanthrene. (Source: EUGRIS Glossary)

the Pan-European Ecological Network (PEEN) is one of the implementation tools of the Pan-European Biological and Landscape Diversity Strategy (PEBLDS). PEEN aims to link the different European and national protected areas and ecological networks with goal of ensuring the favourable conservation status of Europe’s key ecosystems, habitats, species and landscapes.

Ecological network is a system of the most valuable sites, important for protection of threatened species, habitat types, ecological systems or landscapes. Ecological network sites must be relatively close to each other and connected with corridors, which allow them to communicate and exchange species.

Ecological networks contain four main elements:

1. Core areas: These are areas where the primary function is biodiversity conservation. They are usually legally protected under national or European legislation (e.g. Natura 2000 sites). These areas should provide a substantial representation of key natural or semi-natural ecosystems and contain viable populations of important or threatened species. Land use within these areas is managed to give priority to biodiversity conservation.

2. Corridors: These are areas of suitable habitat that provide functional linkages link between core areas. For example, they may stimulate or allow species migration between areas. Corridors can be continuous strips of land or ‘stepping stones’ that are patches of suitable habitat. Using corridors to improve ecological coherence is one of the most important tools in combating the fragmentation that is threatening so many of Europe’s habitats. Generally speaking corridors can be associated with higher levels of land use, as long as their function is maintained.

3. Buffer zones: Protected areas should not be considered as islands that are safe from negative external effects. The resource use that occurs outside them can have serious impacts on species and habitats within, for example air/water pollution from industrial activities around a protected area can have serious effects on species inside it. Buffer zones allow a smoother transition between core areas and surrounding land use. The size and utilisation of buffer zones depends heavily on the particular needs of the specific ecosystem and its local population.

4. Sustainable use areas: These are remaining areas that can come under more intensive land use. But they should still take full account of the successful provision of ecosystem goods and services.

Connecting organisations

• ECNC-http://www.ecnc.org
• IUCN Programme Office for Central Europe-http://www.iucn-ce.org
• Database of Central and Eastern European Ecological Networks
• Plantlife International - http://www.plantlife.org.uk/international/plantlife-ipas.html
• Council of Europe
• IUCN WCPA - http://www.iucn.org/themes/wcpa/
• IUCN CEM - http://www.iucn.org/themes/cem/

Source: http://www.countdown2010.net/archive/paneuropean.html

Personal Computer

polychlorinated dibenzofurans, see polychlorinated dibenzodioxins and polychlorinated dibenzofurans

Personal Computer Memory Card International Association

Personal Digital Assistant

perstane is a new peracid disinfectant (Perestane®). This is an equilibrium mixture of mixed acids and peracids, hydrogen peroxide, and water, together with stabilisers. It is a rapid acting oxidising biocide with a slightly fruity odour. It is particularly suitable for applications involving open handling. It is an effective biocide and can be formulated to provide the desired performance benefits in many uses. The formulations can be thickened, coloured and perfumed. It is decomposing after use to readily biodegradable species.

Properties: it is a 4% peracid product. The major components are listed below:

Peracid content: 4%

Hydrogen peroxide: >10%

Methanol: 3–10%

pH ~1

Perestane® has recently been tested independently and found to be effective against both MRSA (Methicillin Resistant Staphylococcus aureus) and Clostridium difficile.

It is classified as:

Muta. 2 H341 (DSD: Muta. Cat. 3; R68)

Skin Corr. 1B H314

Acute Tox. 4 * H332

Acute Tox. 4 * H312

Acute Tox. 4 * H302

Annex XV. Report has been prepared and STOT-SE 2 H371 recommended instead of Muta. 2 H341Muta. 2 H341

Sources:

http://echa.europa.eu/doc/consultations/cl/CLH_AXVREP_UK_PERESTANE.pdf

http://www.healthcare-inorganics.com/Products/perestane/perestane/0,,58880-2-0,00.htm

periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. It serves as an important food source for invertebrates, tadpoles, and some fish. It can also absorb contaminants; removing them from the watercolumn and limiting their movement through the environment. The periphyton is also an important indicator of water quality; responses of this community to pollutants can be measured at a variety of scales representing physiological to community-level changes.

permeable reactive barriers (PRBs) are applied for passive in situ groundwater remediation. PRBs enable physical, chemical or biological in situ treatment of contaminated groundwater by means of reactive materials, which are filled into the permeable barrier, which the groundwater flows through. The reactive materials are placed in underground trenches or reactors downstream of the contamination plume, forcing it to flow through them. The two main types of PRBs are continuous reactive barriers enabling a flow through its full cross-section, and "funnel-and-gate" systems in which only special "gates" are permeable for the contaminated groundwater. Generally, this cost-effective clean-up technology impairs the environment much less than other methods, being a so called passive technology, without using energy (no pumping, no injection, no heating, minimal care on technolgy maintenance.

persistence is the capacity of a substance to remain chemically stable. This is an important factor in estimating the environmental effects of substances discharged into the environment. Certain toxic substances (e.g. cyanides) have a low persistence, whereas other less immediately toxic substances (e.g. many organochlorines) have a high persistence and may therefore produce more serious effects.

persistent and very persistent substances are which persist in the environment for a long time. The cause for that is, that the substance is not degradable by light or other radiation, heat, oxygen, water or moisture nor on biological effects. Many of the xenobiotics are designed to be persistent in the environment (similar to drugs in the body), otherwise the amount to be applied and as a consequence the cost of the substance would be very high, while the efficiency , due to too short contact-time and not stable concentration would be limited.

Hazard and persistency together increase the risk of the substance, given as ecosystem or humans are exposed for longer time to the substance, so it has higher chance to effectuate its harm.

According to REACH regulation substance fulfils the persistence criterion when:
– the half-life in marine water is higher than 60 days, or
– the half-life in fresh- or estuarine water is higher than 40 days, or
– the half-life in marine sediment is higher than 180 days, or
– the half-life in fresh- or estuarine water sediment is higher than 120 days, or
– the half-life in soil is higher than 120 days.

Annex XIII of REACH defines criteria for the identification of substances that are Persistent, Bio-accumulative and Toxic (PBTs) and Annex I lays down general provisions for PBT assessment. PBTs are substances of very high concern (SVHC) and may be included in Annex XIV and by that be made subject to authorisation (Source: REACH)

PET, the material of plastic bottles, is chemically polyethylene terephthalate, it contains no phthalates. Phthalates (i.e., phthalate ester plasticizers) are not used in PET, and PET is not a phthalate. Plasticizer phthalates are sometimes used to soften other types of plastic, but they are not used in PET. Some consumers may have incorrectly assumed that PET is a phthalate because PET's chemical name is polyethylene terephthalate. Despite the suffix, PET is not a phthalate. Phthalates are low molecular weight monoesters made from ortho-phthalic acid. By comparison, PET is a high molecular weight polyester made from tere-phthalic acid. Chemically they are very different.

Scientific studies documenting the widespread occurrence of low levels of endocrine disrupting compounds (‘EDC’s) in the environment and the food supply have triggered public concern and media attention. Among those are substances of natural origin or of industrial source which are known to be able to bind to estrogen receptors and thus may –theoretically – act in an organism in the same or a similar way as estrogens do. The scientific discussion about it is already going on for years. Up to now there is no clear evidence as to actual influence on humans.

Water samples from PET-bottles tested in an in vitro test system (YES assay) showed the presence of substances with a hormonal effect which were not identified more specifically. The scientists state that the effect was in particular detected in samples packaged in bottles made of the plastic PET. This has raised questions from the public about the possible effects on health of drinking mineral water from PET bottles.

The study from Goethe University Frankfurt highlights migration from packaging (namely PET) as a significant contributor to the measured estrogenic activity of the tested natural mineral waters. However the results presented are not sufficient to demonstrate such a contribution from the packaging since no compounds were identified, nor measured in the samples, and in addition, similar estrogenic activities were sometimes observed in the same water bottled in either glass or PET packaging. In the absence of detection and quantification of EDC’s or estrogenic substances, the observed estrogenic activity cannot simply be attributed to PET packaging.

The level of estrogenic activity detected in the study, if confirmed, would be in the range of nanograms (billionth of a gram per litre). Such activity resulting from the consumption of the tested waters would represent less than a thousandth of the total estrogens produced endogenously in the body and about one millionth of the allowed EU limit of 60 mg for total migration from packaging.

Sources:

http://www.petcore.org/content/does-pet-contain-phthalates

http://www.napcor.com/pdf/BfR_Assessment.pdf

http://www.napcor.com/pdf/EFBWstatement.pdf

polyethylene terephthalate (PET) is one of the most commonly used food grade packaging plastics due to it's chemical inertness and appealing physical properties. as with most plastics PET is derived from oil and is formed by a polymerisation reaction between an acid and an alcohol. its initial uses were as a synthetic fibre with excellent wash and wear properties as well as a substrate for video, photographic and x-ray film. as its use grew PET was modified for application in injection moulded and extruded products, and in the early 1970's the first three dimensional structures were produced by blow moulding techniques, initiating the rapid adoption of PET as a material for beverage bottles. Its properties as a lightweight, tough material with excellent optical properties and adequate gas barrier performance for the retention of PET bottles are manufactured by the process of injection stretch blow moulding (read more at http://www.bpf.co.uk) which was developed specifically to maximise the beneficial properties of PET. PET bottles are manufactured by the process of injection stretch blow moulding (read more at http://www.bpf.co.uk) which was developed specifically to maximise the beneficial properties
of PET.

Source: http://www.designboom.com/contemporary/petbottles.html

PFOA = Perfluorooctanoic Acid, a xenobiotic compound (does not occur naturally in the environment).

PFOA (also known as "C8") is used to make fluoro-polymers for use in non-stick cookware (teflon) and all-weather clothing.

Name and other identifiers of the substance
Chemical Name: Perfluorooctanic acid (PFOA)
EC Name: Pentadecafluorooctanoic acid (PFOA)
CAS Number: 335-67-1
IUPAC Name: Pentadecafluorooctanoic acid

Composition of the substance
Chemical Name: Perfluorooctanic acid (PFOA)
EC Number: 206-397-9 (PFOA)
CAS Number: 335-67-1 (PFOA)
IUPAC Name: Pentadecafluorooctanoic acid

Molecular Formula: C8HF15O2 (PFOA)
Molecular Weight: PFOA: 414.09
Typical concentration (% w/w): 98% , impurities: not known.

Physical state at 20°C and 101.3 KPa PFOA is a solid.
Melting/freezing point PFOA: 52–54 ^oC, PFOA: 54.3 ^oC
Boiling point PFOA: 189 ^oC, PFOA: 189–192 oC/736 mm Hg
Density/specific gravity. 1.792 g/ml
Vapour pressure (Pa) PFOA: 4.2 (25 ^oC) extrapolation from measured data PFOA: 2.3 (20 ^oC) extrapolation from measured data PFOA: 128 (59.3 oC) measured
Surface tension NO DATA
Water solubility (g/L) NO DATA
Partition coefficient noctanol/water NO DATA
Flash point NO DATA
Flammability NO DATA

Dissociation Constants: pKa = in 50% aqueous ethanol pKa = 2.5
pH: 1 g/l (20 ^oC) and 1 g/l (20 ^oC)

Recently, scientists have found great concern about how exposure to PFOA could affect people's health. Both US-EPA and European ECHA is dealing with the risks of this compound. The growing number of results led to the classification of PFOA as hazardous substance together with APFO (the ammonium-derivatiove of PFOA).

PFOA persists indefinitely in the environment. It is a toxicant and carcinogen in animals. In people, it is detected in the blood of general populations in the low and sub-parts per billion range. Chemical plant employees and surrounding subpopulations have been identified with higher blood levels. Exposure is most consistently associated with increased cholesterol and uric acid levels, but there is insufficient evidence to conclude that PFOA exposure results in adverse health effects in people.

As a result of a class-action lawsuit and community settlement with DuPont, three epidemiologists are conducting studies on the population surrounding a chemical plant that was exposed to PFOA at levels greater than in the general population. If PFOA exposure is found to be likely to lead to an increased risk of disease, future liabilities for DuPont will be triggered. Full results from the studies are expected in 2012.

How general populations are exposed to PFOA is not completely understood. PFOA has been detected in industrial waste, stain resistant carpets, carpet cleaning liquids, house dust, microwave popcorn bags, water, food, and PTFE. Although some cookware is marketed as PFOA-free, PTFE non-stick cookware is considered an insignificant exposure pathway.

Toxicity

PFOA is a carcinogen, liver toxicant, a developmental toxicant, an immune system toxicant, and also exerts hormonal effects including alteration of thyroid hormone levels. Animal studies show developmental toxicity from reduced birth size, physical developmental delays, endocrine disruption, and neonatal mortality. PFOA causes liver cancer in rodents and also induces testicular and pancreatic cancer through induction of Leydig cell tumors and pancreatic acinar cell tumors. PFOA alters lipid metabolism. It is an agonist of PPARα and is a peroxisome proliferator in rodents contributing to a well understood form of oxidative stress. Humans are considered less susceptible to peroxisome proliferation than rodents. However, PFOA has been found to be a liver carcinogen in rainbow trout via a potential estrogenic mechanism, which may be more relevant to humans.[91] A study found PFOA to be an obesogen in female mice at mid-age—with altered levels of insulin and leptin—at the lowest dose of 0.01 milligrams per kilogram of body weight during development.

While a USEPA review notes PFOA has not "been shown to be mutagenic in a variety of assays" in 1991 researchers from Japan demonstrated oxidative liver DNA damage in an experiment with rats. PFOA has been described as a member of a group of "classic non-genotoxic carcinogens". However, a provisional German assessment notes that a 2005 study found PFOA to be genotoxic via a peroxisome proliferation pathway. A 2006 study demonstrated the induction and suppression of a broad range of genes; therefore, it states that the indirect genotoxic (and thus carcinogenic) potential of PFOA cannot be dismissed. Criteria have been proposed that would allow PFOA, and other perfluorinated compounds, to be classified as "weakly non-specific genotoxic."

Epidemiology

The levels of PFOA exposure in humans vary widely. While an average American might have 3 or 4 parts per billion of PFOA present in his blood serum, individuals occupationally exposed to PFOA have had blood serum levels over 100,000 parts per billion (100 parts per million or 0.01%) recorded. In a study of individuals living around DuPont's Washington Works WV plant, those who had no occupational exposure had a median blood serum level of 329 parts per billion while the median of those with occupational exposure was 775 parts per billion. While no amount of PFOA in humans is legally recognized as harmful, DuPont was "not satisfied" with data showing their Chinese workers accumulated an average of about 2,250 parts per billion of PFOA in their blood from a starting average of around 50 parts per billion less than a year prior.

Single cross-sectional studies on consumers have been published noting multiple associations. Blood serum levels of PFOA were associated with an increased time to pregnancy — or "infertility "— in a 2009 study. PFOA exposure was associated with decreased semen quality, increased serum alanine aminotransferase levels, and increased occurrence of thyroid disease. In a study of 2003–2004 US samples, a higher (9.8 milligram per deciliter) total cholesterol level was observed when the highest quartile was compared to the lowest. Along with other related compounds, PFOA exposure was associated with an increased risk of attention deficit hyperactivity disorder (ADHD) in a study of US children aged 12–15.[103] In a paper presented at the 2009 annual meeting of the International Society of Environmental Epidemiology, PFOA appeared to act as an endocrine disruptor by a potential mechanism on breast maturation in young girls. A C8 Science Panel status report noted an association between exposure in girls and a later onset of puberty.

PFOA has been associated with signs of reduced fetal growth including lower birth weight.However, other studies have not replicated the lower birth weight finding including a study on the DuPont exposed community.PFOA exposure in the Danish general population was not associated with an increased risk of prostate, bladder, pancreatic, or liver cancer.Maternal PFOA levels were not associated with an offspring's increased risk of hospitalization due to infectious diseases, behavioral and motor coordination problems, or delays in reaching developmental milestones.

Regulation

On January 15, 2009, the USEPA set a provisional health advisory level of 0.4 parts per billion in drinking water. On March 1, 2007, the Minnesota Department of Health lowered its Health Based Value for PFOA in drinking water from 1.0 parts per billion to 0.5 parts per billion, where "the sources are landfilled industrial wastes from a 3M manufacturing plant."

PFOA contaminated waste was incorporated into soil improver and spread on agricultural land in Germany, leading to PFOA drinking water contamination of up to 0.519 parts per billion. The German Federal Environmental Agency issued guidelines for the sum of PFOA and PFOS concentrations in drinking water: 0.1 parts per billion for precaution and 0.3 parts per billion for a threshold. Residents were found to have a 6–8 factor increase of PFOA serum levels over unexposed Germans, with average PFOA concentrations in the 22–27 parts per billion range. An expert panel concluded that "concentrations were considered too low to cause overt adverse health effects in the exposed population."

In 2011 European Union started with the classification of PFOA and APFO on the initiative of the Climate and Pollution Agency (Norway), who prepared the CLH report for PFOA.

The recommendation of Norway is the following classification of PFOA as carcinogenic, reprotoxic, toxic for specific target organs, acutely toxic and eye irritant:

Carc. 2, H351
Repr. 1B, H360D
STOT RE 1, H372
STOT RE 2, H373
Acute Tox. 3, H331
Acute Tox. 3, H301
Eye Irrit. 2, H319

Pictogram: GHS07, GHS08
Signal word: Danger

Hazard statement codes: H351, H360D, H372, H373, H331, H301, H319
Precautionary statements: Not required as PS are not included in Annex VI

Sources:

http://echa.europa.eu/doc/consultations/cl/clh_axrep_pfoa.pdf

http://www.pfoa.com/

http://en.wikipedia.org/wiki/Perfluorooctanoic_acid