HealthyLifeDigest: 3/22/09

There are seven type of plastic polymers used for food-drink packaging,

many of their additives as well as monomers impurities are harmful for health.

The plastic resin identification codes

Plastics play many important roles in life on earth, but the widespread use of plastics are also causing environmental problems, and harmful for health, chemicals leached from plastics used in cooking and food / drink storage are harmful to human health, the most disturbing of these are hormone disrupters, like Bisphenol A (BPA), which can stimulate the growth of cancer cells, exposure to BPA at a young age can cause genetic damage, the health risks of plastic are significantly amplified in children, whose immune and organ systems are developing and are more vulnerable, plastic should be used wisely, with caution and only when suitable alternatives do not exist or available.
Plastic packaging polymers (resins) which are safe for food and beverages are type No.1 (PET / PETE), No.2 (HDPE), No.4 (LDPE), No.5 (PP). which are not safe for foods and beverages are type No.3 (PVC), No.6 (Polystyrene), and No.7 (others / Polycarbonate).

Recycle of used plastic packaging :

Consumers have a way to identify the type of plastic in many products, especially food storage containers and packaging, the resin identification code in molded formed or imprinted on the bottom of plastic containers. This system of coding was developed in 1988 by the U.S.based Society of the Plastics Industry to facilitate the recycling of post-consumer plastics, it is voluntary for plastic manufacturers, but has become relatively standard on certain plastic products sold globally, unfortunately, as a matter of fact, many plastic products have not yet bearing the resin identification code.

platic polymer / resin identification codes imprinted

at the bottom of plastic bottles

Use of the resin identification codes:

For consumers, by knowing the resin identification code for particular plastic products, consumers can then inform themselves of the characteristics of the plastics and the risks of using that products.
For plastic recyclers, in the process of recycling, plastic packaging should be separated in groups based on their type of resins (polymers) and their colors,

Recycled plastic packaging are prohibited for re-packing foods and beverages, they are used for other purposes, use only genuine plastic polymers for foods, drinks, drugs / medicines, medicinal devices, and cosmetics.

Polymer chemical compounds can be classified into:

1. Natural polymers: shellac, amber.

2. Biopolymers: proteins, DNA, cellulose.

3. Synthetic polymers: plastics, silicones, nylon, polyacrylonitril.

Plastics are synthetic polymer products, the results polymerization (polycondensation) of the monomers depending on the type of plastics, monomers are nsaturated hydrocarbon chemical compounds, have a double bond between their two carbon atom (double bond chain), called Alkene or olefine, monomers for plastic manufacturing are ethylene, propylene, vinyl-chloride, styrene etc.

Plastic polymers can be divided into two groups:

Polyolefins: polymerization of alkene or olefine,

HDPE (High Density Polyethylene) – Recycle code No.2: HDPE is flexible, more rigid than LDPE, good impact strength and stress crack reesistence, good chemical resistance, good vapor barrier. Common uses: plastic bottles and jars for drinking water, foods, milks, juices, cosmetics, detergents and shampoo bottles.
PVC (Polyvinyl Chloride) – Recycle code No.3: PVC is flexible to rigid, good for coating, fair water vapor barrier but good oxygen barrier, good chemical resistance, good impact and some stress crack resistance, poor recycling due to chloride residues. Common uses: clear foods and non foods packaging (cling-wrap), squeeze bottles, shampoo bottles, cooking oils, peanut butter jars, medical tubing (medical devices), detergents, glass cleaner bottles, shower curtains, numerous construction products (wire insulations, pipes, sidings). Leaches di(2-ethylhexyl) phthalate (DEHP) or butyl benzyl phthalate (BBzP), depending on which is used as the plasticizer or softener in the manufacturing. PVC has been described as one of the most hazardous consumer products ever created
LDPE (Low Density Polyethylene) – Recycle code No.4: LDPE is very flexible, natural milky color, translucent with high impact strength, good chemical resistance, good water vapor and alcohol barrier properties, poor gas barrier, hood stress crack and impact resistance. Common uses: squeezable bottles for honey, mustard, for bread and food bags, used in grocery store, dry cleaning, most plastic wraps.
PP (Polypropylene) – Recycle code No.5: PP is rigid, solid, durable in container or cap forms, opaque, natural grayish yellow in natural form, excellent stress crack and impact resistance, PP botlles and jars have excellent moisture barrier, good oil and alcohol barriers, poor gas barrier properties, good chemical resistance. Common uses: plastic containers for ketchups, yogurts, syrup bottles, drinking straws, baby bottles, margarines tubs, medicines.
PS (Polystyrene) – Recycle code No.6: PS is transparent, rigid and glasslike polymer, light and heat stable, biologically inert and non-toxic, good resistance to inorganic chemicals, PS containers have good impact and stress resistance, poor barrier properties. Common uses: Styrofoam containers, food plates, take-out food containers, disposable cups and bowls, packaging for CDs (compact disc cases), egg cartons, plastic cutlery. Leaches styrene, which is an endocrine disruptor mimicking the female hormone estrogen, and thus has the potential to cause reproductive and developmental problems.
Other (miscellaneous classification) - Recycle No.7: it includes:

PC (polycarbonate), a dangerous plastic, the new, safer, Common uses of PC bottles: plastic bottles for squeezable ketchups and syrups, juices, used in most plastic baby feed bottles, clear plastic sippy cups, drinking water bottles, large water storage containers, metal food can liners, compact discs, cell phones, computers. Leaches Bisphenol-A an hormone (endocrine) disrupters. Plastic bottles and plastic containers from this group are not easily recyclable
Bioplastics: Biodegradable bio-based plastics (Plastarch material – PSM) & Polylactic acid or polylactide (PLA) made from renewable resources such as corn and potato starch, and sugar cane, the new safer plastic products.
PTFE (Polytetrafluoroethylene), known as Teflon.
Acrylonitrile styrene (AS) or styrene acrylonitrile (SAN), and Acrylonitrile butadiene styrene (ABS). Both AS/SAN and ABS are higher quality plastics with increased strength, rigidity, toughness and temperature and chemical resistance. AS/SAN is used in mixing bowls, thermos casing, dishes, cutlery, coffee filters, toothbrushes, outer covers (printers, calculators, lamps), battery housing. The incorporation of butadiene during the manufacture of AS/SAN, produces ABS, which is an even tougher plastic. ABS is used in LEGO toys, pipes, golf club heads, automotive parts, protective head gear.

Polyester: polymerization of esters

PET / PETE (Polyethelene Terephthalate) – Recycle code No.1; PET or PETE is semi-rigid to rigid depending on container’s wall thickness, good to fair chemical barrier, not good for strong acids and bases (alkali), good solvent and alcohol barrier, good gas and fair moisture barrier, good moldability. PET / PETE bottles and jars have good stress crack and impact at room temperature. Common uses: bottles for drinking waters, soft drinks, sodas, beers, juices, foods, salad dressings, edible oils, peanut butters, cereal box liners, mouthwashes, lotions, liquid soaps / detergents, cleaning agent containers. Leaches Antimony trioxide.
PBT (Polybutylene Terephthalate) – Recycle code No.1: good chemical resistance, clear color, resistance to water, weak acids and bases at room temperature.
Polyester fabrics.
Polyester fibers.

Harmful chemical compounds in the plastic products:

In the process of polymerization (poly-condensation) there are possibilities of some monomers which are not bound into polymer molecules (macro-molecules), so that they remain as monomer-free compounds in the plastic products.
There are three compounds in plastic products:

Polymer compounds: poly-olefins, or polyesters. International Agency for research on Cancer (IARC) studies on carcinogenicity of plastic polymers on animals indicate that plastic polymers are not inherently carcinogenic or genetotoxic. Plastic Polymers are biologically inert due to high molecular weight.
Additives (chemicals added to improve the nature of plastics themselves.
Monomers impurities.

Many additive chemical compounds used for plastic manufacturing are harmful for human health, they can leach into foods, drinks etc.

Additives for plastics manufacturing are classified based on their functions:
Additives are not part of the polymers matrix, they may migrate out of the plastic surface, the extent of migration is usually enhanced by temperature, additives are usually made up of small molecules which may be absorbed into the human body, some additives are very toxic, lead (Pb) and cadmium (Cd) containing stabilizers have potential adverse human, and eco-toxicological effect, now they are currently being phased out and replaced by stearate and oleate salt of Barium (Ba), Zinc (Zn), Calcium (Ca) system. Lubricants as plastic additives generally do not pose human hazard unless they contain heavy metals. (see Lead-stearate as lubricant). Plasticizers phathalate and adipates as plastic additives are commonly used in PVC manufacturing, they can easily off-gas and migrate into fatty foods when foods are wrapped in PVC, high dosage of phthalates and adipates may cause testicular atrophy, decrease spermatogenesis and lower fertility.

1. Stabilizer:

· Lead compound, compound Lead / Plumbum (Pb): lead-oxides, lead-sulphates, lead-phosphates.

· Cadmium compound (Cd).

· Metal-soap-compound: Zn, Ca/Zn, Ba/Zn, Ba/Cd- stearates and oleate.

· Organic tin compounds (Zn / tin), such as dimethyl-tin-thioglycolate.

2. Palsticizers:

· Phathalates: Diethylhexylphthalate (DEHP), Dioctylphthalate (DOP)

· Adipates: Diethylhexyladipate (DEHA),

· Bisphenol (BPA), used in Polycarbonate baby bottles.

3. Lubricants:

· Lead-stearate,

· Stearic-acid (waxes),

· Mineral-oil.

4. Catalysts:

· Hydrogen peroxide (H₂O₂)

· Ethyl-chloroformate,

· Methylethyl-ketone peroxide,

· Antimony-based catalyst used in the manufacturing of PET bottles.

5. Others additives:

· Pigments: should be food grade (FDC).

· Fillers: talc, titanium-dioxide (TiO₂).

· Bacteriostatics.

· UV radiation absorbers.

· Antistatic agents

· Surfactants.

Additives should be considered carefully, some of them are very toxic, consideration must be made to :

· Length of food exposure,
· rate of additives and residues migration into foods,
· possibility of accumulation.

Monomers impurities: ethylene, vinyl-chloride, propylene, styrene.

Some plastic monomers (residue / impurities in plastic manufacturing – during polymerization process) may pose hazards, in some plastics, residues are negligible, but in others they are significant, especially if the molecular weight of the plastic polymers are small, most monomers are not appreciably absorbed through skin, but can be absorbed very well by lung and gastrointestinal tract. Vinyl-chloride monomer (VCM) causes liver cancer, also causes skin and lung tumor, depression of central nerve system (CNS) at dosage of 8000-10.000 ppm. Ethylene and propylene monomers are not genetotoxic. Styrene are strongly genetotoxic when metabolized to styrene-oxide, styrene may also be carcinogenic to human.

Various plastic containers for drinking water sold in the market:

· No.1 (PET / PETE) for drinking water packaged in plastic bottles of 600 ml – 1000 ml.

· No.5 (PP) for drinking water packaged in plastic glass or plastic cup of 250 ml.

· No.7 (Other) for drinking water packaged in plastic gallon container of 20 liters

· No.2 (HDPE) for bottles and gallon plastic caps.

How to use safely plastic food-drink containers?

Drinking water, try and avoid plastic bottles, use glass bottles or stailess steel bottles, if use plastic bottles made from #1(PET / PETE) or #2 (HDPE) plastic try not to reuse them, and consume the contents as soon as possible because leaching of antimony increases with time.
Do not use plastic dishes and utensils for meals, as alternatives use glass, ceramic, wood, stainless steel, and lacquer ware.
Do not heat foods in plastic containers, especially in the microwave oven, which can cause the plastic to degrade and leach chemicals faster, leaching increases when plastic comes into contact with oily or fatty foods, or when the plastic is scratched, worn, cracked, or sticky.
Do not use PC (polycarbonate) baby bottles, try to use glass, polyethylene, or polypropylene, check the bottle to be sure of the type of plastic code it contains. for baby bottle nipples, try and use silicone which does not leach the carcinogenic nitrosamines that can be found in latex, if has to use PC (polycarbonate) bottles, do not heat the foods and drinks in the bottle, heat them in a separate containers and then transfer them to the bottle once it is warm enough for the child to eat or drink, if the PC plastic bottles are showing signs of wears or scratched, cloudy, do not use but discard the container, replace with the new one.
Use sippy cups made of stainless steel, or made of polypropylene or polyethylene.
Use plastic wraps with caution, especially in the microwave, and try to keep the plastic from touching the food, as safer alternatives are using wax paper.

Stainless steel and glass food storage containers are the best for use.

Continued with Related Articles:

· PET / PETE Bottle, its advantages, and its Health issues

· Safely use of Polycarbonate Baby Feed Bottles

· Safely use of Polystyrene Food Plates

. Bioplastics