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Materials discussed: Polycarbonate, LDPE, HDPE,
Silicone, Glass, Stainless Steel, cast iron, Polyether Sulfone. (Styrene is not
discussed; it is probably unsuitable for any food-handling
application.)
* list of plastics and their recycle numbers
for identification
* References
* Letter to Sigg (Swiss sports bottle manufacturer)
11/25/2005: Sigg's reply, and our comments and results of a quick online
search.
A very brief history of toxicology
Discussions of toxicity were originally limited to acute toxic effects,
i.e., obvious poisoning, and were measured by the death rates of experimental animals,
which tend to occur with relatively high doses of even acutely
poisonous compounds. Later, research on carcinogenicity and direct effects on
genetic material focused the discussion on considerably lower dosages,
since effects at the level of the cell nucleus and DNA were more subtle
and sensitive. It appears that the developing fetus or newborn is even
more sensitive, exhibiting effects at extremely low concentrations of some
bioactive substances. The Nalgene website, in disputing the information
reviewed here, disengenuously cites oudated research using testing methods that were able
only to detect very high levels of leachates.
Polycarbonate
It has recently come to my attention that some of the products I have
suggested as a substitute for PVC may not in fact be safe or suitable for
food or water containers. The biggest offender is polycarbonate (Lexan). I
have to confess I have used a Nalgene ploycarbonate bottle for hiking for
a few years, and in winter for carrying hot water. Following is the result
of a quick but fairly thorough reading through scholarly findings
(peer-reviewed scientific journals), as opposed to information obtained
through advocacy organizations.
As a by-the-way, if any more about
this were needed, the phthalates found in PVC (polyvinychloride or
Vinyl) may be considered harmful to
fetuses and young infants in any concentration; PVC's are suitable, if at
all, only for older children, and probably not for food contact for
anyone.
Relevant to discussions elsewhere regarding
PVC, a study of additives in plastics found that not all phthalates (the plasticizing
compounds used in PVC) were found to be estrogenic4. However, since it is
hard to determine which ones are used in any particular consumer product,
PVC's are still best avoided for any kind of use with infants under 12 months, or for
products that will be put in the mouth up to age 12. Maybe it is best to
avoid PVC for eating or food handling altogether.
Polycarbonate (Lexan) is used extensively in food-contact utensils,
including baby bottles, sports water bottles, food containers, and
tableware. Its basic monomer is Bisphenol A, originally synthesized in the
1930's as an estrogen agonist (booster or mimic) for pharmacological use. Only later was it used in
the plastics industry. The fragility of the polymer structure results in
significant leaching of Bisphenol A into a variety of substances.
Bisphenol A has been shown to be an endocrine disruptor and to simulate
the action of estrogenc compounds. These effects are dissimilar to other
kinds of toxicity, in that very small dosages, resulting from
concentrations too low to measure until the relatively recent advent of
more sophisticated assay methods, may strongly affect reproductive system
development in male fetuses during certain sensitive developmental windows1.
Exposure to Bisphenol A may cause a hyperdevelopment of the male reproductive system that may
predispose to prostate enlargement. Such effects are also seen in adult
male mammals. There is also evidence that Bisphenol A enhances growth of
human breast cancer cells. Bisphenol leaching is considerably greater in
Polycarbonate that is scratched, cloudy, or exhibits wear of any sort.
Heating also accelerates the leaching process, so carrying hot water in a
polycarbonate bottle is a very bad idea.
Polyethersulfone (PES) looks promising as the
long-awaited plastic with all the properties one could wish for. A relatively new polymer, Polyethersulfone, or PES, is
now being used by a few manufacturers as a replacement for polycarbonate. A
brief review of suppliers' and academic websites reveals no evidence that
plasticizers or stabilizers are needed for this polymer. It is strong,
clear, tough, and very heat resistant. PES can be boiled repeatedly with
no degradation, so it is useful for baby bottles. It is so chemically inert and non-toxic that it is used for laboratory-grade
filters. It requires no additives.
I have found a company
that makes PES baby bottles with medical grade silicone nipples (http://www.greentogrow.com
). Olefins: Polyethylene & Polypropylene
Additives in LDPE (low-density polyethylene) & HDPE (high-density
polyethylene) are primarily antioxidants, such as
Irganox or BHT2. There is little information on the toxicity (inluding
endocrine disruption) of these compounds, but we could find no evidence of
toxicity in the literature. There is some evidence that they are not endocrine disruptors or
estrogen mimics. ("polyalkylated, hindered phenols like BHT and
Irganox 1640 are not estrogenic, while
being effective antioxidants..." 4
Interestingly, there is some recent
work developing tocopherols (Vitamin E) as antioxidants for HDPE &
LDPE.
Migration into water and food substances have been measured for these
antioxidants, generally at higher temperatures than experienced in
normal use. At high temperatures, and especially with fatty or oily
foods, there is considerable loss of antioxidants. These plastics should
thus be used primarily with cold water, to reduce migration to a
minimum. Washing agents and other substances used in the manufacture of
the polymer may be present, but can be removed with thorough washing of
the new plastic product. HDPE generally exhibits the least migration of
antioxidants3. Nonetheless, there is evidence of migration into food
products, even dry foods. Stabilizers in Polypropylene have been found
to be biologically active (potentially affecting nerve transmission) and
to leach from the plastic5.
Silicone Rubber
Silicone Rubber is regarded by some as the answer
to the toxicity problems of other plastics used for juvenile products such as
teethers and bottle nipples. Ideally, this material can be made with no
additives or uncured monomer or oligomer that will leach out in use.
Medical grade Silicone is made with the platinum-catalyzed curing process,
and can be free of any migrating substances. It is generally more
expensive. There are a variety of other curing processes.
Additionally, silicone is produced with a large variety of additives, for
color, strength, stiffness or elasticity, and resistance to degradation,
and silicone can be copolymerized with other plastics, including PVC.
Tested samples of products have even contained phthalates 6,7. Nipples in the latter
study7
leached no substances at all into the test solvent.
Glass, Porcelain, Stainless Steel, and Cast Iron
These materials come closest to being truly
inert and refractory in the solvent environment found in food handling
and saliva (food preparation, storage, eating utensils). However,
there is data showing that even they are not perfect. The toxic
nickel in Stainless may be leached by cooking with acid foods (apple
juice is very acidic). Glass is formulated in a large variety of ways,
and may leach alkaline substances or metals. Cast Iron in
old-fashioned cookware can be regarded as entirely safe. Iron
generally does not add toxicity to compounds, unless the dosage is very
high (especially in men). It is, in fact, an important nutrient. Properly
seasoned and well-maintained iron cookware can be regarded as safe for any
cooking or storage use, even at high temperatures. A high-fired
porcelain-coated iron utensil ("real" porcelain) would be as
safe or safer. Of course, such utensils are heavy, and unsuitable
for carrying food.
As an aside, the modern synthetic coatings used
on some branded cookware may become hazardous at temperatures that are
significantly higher than their recommended operating range. There is at
least one report of harm resulting from abuse or burning of a
"high-tech" coated cookware utensil.
The conclusion to be drawn from this is that although plastic for
food contact has advantages in light weight, break-resistance, and cost,
its use is best restricted to cold foods and liquids. Since most
plastics additives are especially soluble in fats and oils, fatty foods might
better be wrapped in aluminum foil, even if it is then placed in poly
bags. Polyolefins, including polypropylene and polyethylene (preferably
HDPE), are the safe choices, although they also share some of the
undesirable qualities of other polymers, perhaps less problematically.
Silicone nipples of high quality (medical grade) are probably the best
choice for infant bottles nipples and teethers. There are, of
course, a great variety of traditional teethers that get around this
problem entirely, such as toast, a frozen damp washcloth, carrots, and
of course, MY VERY OWN® Rattle,
which we (Turnertoys) make.
There is no question that the best choices
for food storage and handling are and always have been
glass and high-fired ("real") porcelain or stoneware,
with stainless steel a close second. The glazes on cheaper
ceramics may use lead fluxes, since they are fired at low temperatures.
This is common with "hobby" ceramics.
STAINLESS STEEL UPDATE - May 20, 2007:
It looks like the safest choice for sports bottles is still stainless
steel. I found a stainless product called Klean Kanteen that is a
pretty good match for the Nalgene bottles in size and cost. There are a number of websites offering it.
I have been using one for the past 6 months and I think it is
excellent. It holds 40 oz., and weighs just about the same as a 32
oz Nalgene bottle. Look up Klean Kanteen on Google for places to buy one.
A brief online search suggests that storage of cold acidic liquids should not present a problem. A very realistic and, I think, valid-sounding study by the U.K. Laboratory of the Government Chemist concluded that
"... nickel pickup by meal-sized portions of real foods cooked in stainless steel utensils at normal domestic cooking temperatures and times was generally below the analytical detectable limits for nickel of 0.01 mg/kg, or
l µg in a 100 g serving of food. Undetectable nickel pickup is considered insignificant with respect to human health effects and reinforces the
ongoing use of stainless steel by consumers as the material of choice for cookware."
Notably, previously unused utensils leached the most nickel (to be expected), which was negligible to begin with, and rapidly declined from that point. These
results were for hot acidic foods simmered for 1 to 2 hours. Storage of cold liquids presents even less of a problem.
The foods tested in the LGC study -- lemon marmalade, green tomato
chutney, potatoes, rhubarb, and apricots -- were selected
because their acidity or chloride content make them more likely than other
foods to be aggressive against stainless steel. With few exceptions, there
was no detectable nickel pickup, even in the preparation of chutney, which
involved two hours of simmering in vinegar. Some detectable nickel pickup
did occur, however, with rhubarb and apricots cooked in new pots.
Cooking Rhubarb:
| # of Cooking Operations |
Nickel leached: mg/kg n.d. = not
detectable
|
| Pan 1 |
Pan 2 |
Pan 3 |
| 1 |
.08 |
.27 |
.07 |
| 2 |
.07 |
.10 |
.05 |
| 3 |
.04 |
.03 |
.01 |
| 5 |
.03 |
.02 |
.03 |
| 8 |
n.d. |
.02 |
n.d. |
| 16 |
n.d. |
n.d. |
n.d. |
| 20 |
n.d. |
.02 |
.01 |
Another popular alternative to plastic sports bottles is the Sigg
bottle (available just about anywhere online or in stores). They are
aluminum with some kind of coating. I have written to them
requesting information on the composition of that lining (see
below). Update: we have received a reply (see
below). We are still looking into the significance for food
safety of this reply, i.e., what exactly is this polymer and what hazard
it presents, if any.
We now state that Stainless steel is almost totally safe in most uses,
including very hot foods. Acidic foods stored for long periods or cooked in
stainless may leach insignificant amounts of Nickel and Chromium.
The figures for nickel are shown above. Chromium is not toxic
except in larger doses, in people with kidney disorders. Chromium
is an important nutrient that helps stabilize usage of sugars in the
body, and may help to prevent diabetes.
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+++++++++++++++
Email Letter to Sigg Corporation (October 9, 2005):
Dear Sirs,
I am preparing a short article for my website as an update on the safety
of materials used for toys and other products that may come into contact
with food. Up to now this section has provided an extensive reference on the
hazards of PVC, but we have gotten a lot of questions regarding other
polymers. My other interest is as a user of sports bottles for hiking (I
also have a section dedicated to outdoor activities). It appears that the
popular Polycarbonate bottles are unsuitable for food contact. This leaves
only polyethylene, preferably HDPE, stainless steel, and your bottles. Since
it has eventually turned out that almost any synthetic material, however
stable, leaches small quanitities of harmful material, I am wondering what
sort of polymer is used in your bottle coatings. I would prefer to have some
good new to report. Your website states that you use a " baked-on stove
enamel". Are you referring to a ceramic or porcelain material? I
understand the coating is flexible, so it would have to be a polymer of some
sort, presumably synthetic, unless you are using tung oil.
Thanks for your response.
Ed Loewenton
Reply received 10/8/2005:
Hello Ed
Thank you for your request. The SIGG bottles are coated on the inside with an epoxy phenol resin which matches the requirements of the US FDA 21 CFR 175.300. We are testing our bottles frequently at an external laboratory according the FDA regulations. We pass all those tests without any migration of insalubrious substances, such as Bisphenol, BADGE, BFDGE, Aluminum, etc. The inner coating is very flexible, dents have no effect to the inner coating.
For further informations don't hesitate to contact me.
Freundliche Grüsse / Kind regards
Ronald Schindele
Head of Product Development
SIGG SWITZERLAND AG
Walzmühlestrasse 62 , CH- 8500 Frauenfeld
Tel. +41 (0)52 7286330 , Fax +41 (0)52 7286307
Tel. direkt: +41 (0)52 7286369
eMail: Ronald.Schindele@sigg.ch
Besuchen Sie unsere Homepage: http://www.sigg.ch
OUR COMMENTS (11/25/2005):
An online search of "epoxy phenol resins"
has not so far revealed any indications of health hazards resulting from
leaching of additives or polymer degradation byproducts. The material
appears to be quite refractory to breakdown from heat or food acids. The key
phrase is "so far". A quick read through 30 or so documents
revealed the presence of substances that might arguably be harmful, but that
do not appear to leach out of the Sigg bottle coating through breakdown of the polymer in most
consumer applications, such as storage of juices or warm water. There
should be no problem using it as a basic cold water bottle.
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++++++++++++++++++++++++++++++++++
Plastics identification numbers
- #1 - Polyethylene Terephthalate (PET or PETE)
- #2 - High Density Polyethylene (HDPE)
- #3 - Vinyl (Polyvinyl Chloride or PVC)
- #4 - Low Density Polyethylene (LDPE)
- #5 - Polypropylene (PP)
- #6 - Polystyrene (PS)
- #7 - Other (which commonly includes Polycarbonate, ABS, Nylon,
Acrylic or a composite of 2 or more resins)
References:
1. vom Saal, Frederick. Very low doses of bisphenol A and other
estrogenic chemicals alters development in mice. Endocrine Disruptors
and Pharmaceutically Active Chemicals in Drinking Water Workshop, April
19-21, 2000. Chicago, Illinois . Online at http://www.cheec.uiowa.edu/conferences/edc_2000/
An excellent exposition in plain language regarding the
leaching and
harmful effects of monomer from polycarbonates.
2. Till
DE, Ehntholt
DJ, Sidman
KR, Whelan
RH, Schwartz
PS, Reid
RC.
Migration of BHT and Irganox 1010 from low-density polyethylene (LDPE) to
foods and food-simulating liquids.
Food Chem Toxicol. 1987 Apr;25(4):317-26
The most widely used food-wrapping material is low-density polyethylene
(LDPE). Food-wrap grades contain antioxidants to minimize degradation during
processing and, in the final films, such additives are normally present at
levels of several hundred ppm. During use, the antioxidants may migrate into
food stored in LDPE wraps. Two typical antioxidants, BHT and Irganox 1010,
were radiolabelled to allow accurate analytical measurement of the extent of
their migration into foods and food-simulating liquids (FSL). The results
show that BHT, a much smaller and more volatile molecule than Irganox 1010,
migrates more rapidly into foods, but the differences are less for FSL. In
most instances, migration appears to be controlled by diffusion of the
antioxidant in the polymer, and the quantity lost can be correlated in a
linear fashion with the square root of time. With aqueous FSL, and,
presumably aqueous-type foods, however, anomalies result; the migration is
often erratic, but is more closely related to time than to the square root
of time. A tentative model developed to explain these facts assumes that the
antioxidants decompose in aqueous media and the net migration rate is
controlled largely by the rate of chemical decomposition. It is also shown
that dry foods can be surprisingly effective sinks for antioxidants under
typical storage conditions.
3. Marcato, B., Guerra, S., Vianello, M., Scalia, S.,
Migration of antioxidant additives from various polyolefinic plastics
into oleaginous vehicles. International Journal of Pharmaceutics Vol. 257, No. 1, pages
217-225 (2003)
Abstract
The migration of the antioxidant additives pentaerythrityl
tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010) and
tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) from polyolefinic
packaging into oily vehicles was investigated. The polyolefins included in
the study were from the following classes: isotactic polypropylene
homopolymer (PP), ethylene-co-propylene random copolymer (RACO),
ethylene-propylene heterophasic copolymer and ethylene-propylene amorphous
copolymer blend (EP) and high-density polyethylene (HDPE). Each polymer was
additioned with Irganox 1010 (0.15%, w/w) and Irgafos 168 (0.15%, w/w) and
processed into blown bottles. To study the antioxidant release process,
plastic sheets were cut from the bottles and dipped for various time
intervals into a mixture of five oils (caprylic/capric triglyceride,
cyclomethicone, dicaprylyl ether, isohexadecane and
C"1"2"-"1"5 alkyl benzoate) representative of
lipophilic excipients used in pharmaceutical and cosmetic formulations.
After exposure to the oil medium, the non-migrated Irganox 1010 and Irgafos
168 were recovered from the polymeric matrices using microwave-assisted
extraction with ethyl acetate-hexane and assayed by HPLC. The leaching of
the two antioxidants varied remarkably depending on the polyolefin
crystallinity and structure. The amount of Irganox 1010 transferred into the
contact medium at 25^oC decreased in the order EP>RACO>PP>HDPE. The
same polyolefin ranking was observed in the case of Irgafos 168, except for
PP and HDPE which exhibited similar depletion of this additive. Migration of
Irgafos 168 was greater than that of Irganox 1010 and the release of both
antioxidants increased at higher temperature (50^oC). The obtained data are
useful for the selection of polyolefinic matrices as raw-materials for the
production of pharmaceutical and cosmetic containers.
+++++++++++++
4. Ana M. Soto, Carlos
Sonnenschein, Kerrie L. Chung, Mariana F. Fernandez, Nicolas Olea, and Fatima Olea
Serrano.
The E-SCREEN Assay as a Tool to Identify
Estrogens: An Update
on Estrogenic Environmental Pollutants. Environ Health Perspect
103 (Suppl 7):113-122 (1995)
Abstract:
Estrogens are defined by their ability to induce the proliferation of cells
of the female genital tract. The wide chemical diversity of estrogenic
compounds precludes an accurate prediction of estrogenic activity on the
basis of chemical structure. Rodent bioassays are not suited for the
large-scale screening of chemicals before their release into the environment
because of their cost, complexity, and ethical concerns. The E-SCREEN assay
was developed to assess the estrogenicity of environmental chemicals using
the proliferative effect of estrogens on their target cells as an end point.
This quantitative assay compares the cell number achieved by similar inocula
of MCF-7 cells in the absence of estrogens (negative control) and in the
presence of 17ß-estradiol (positive control) and a range of concentrations
of chemicals suspected to be estrogenic. Among the compounds tested, several
"new" estrogens were found; alkylphenols, phthalates, some PCB
congeners and hydroxylated PCBs, and the insecticides dieldrin, endosulfan,
and toxaphene were estrogenic by the E-SCREEN assay. In addition, these
compounds competed with estradiol for binding to the estrogen receptor and
increased the levels of progesterone receptor and pS2 in MCF-7 cells, as
expected from estrogen mimics. Recombinant human growth factors (bFGF, EGF,
IGF-1) and insulin did not increase cell yields. The aims of the work
summarized in this paper were a) to validate the E-SCREEN assay; b)
to screen a variety of chemicals present in the environment to identify
those that may be causing reproductive effects in wildlife and humans; c)
to assess whether environmental estrogens may act cumulatively; and finally d)
to discuss the reliability of this and other assays to screen chemicals for
their estrogenicity before they are released into the environment. --
5. H Glossmann, S Hering, A Savchenko, W Berger, K Friedrich, ML Garcia, MA
Goetz, JM Liesch, DL Zink and GJ Kaczorowski. A Light Stabilizer (Tinuvin
770) that Elutes from Polypropylene Plastic Tubes is a Potent L-Type
Ca2+-Channel Blocker. Proceedings of the National Academy of
Sciences,
Vol 90, 9523-9527 (1993)
A pharmacologically active agent was easily extracted by aqueous or
organic solvents from laboratory plastic tubes (Falcon Blue Max) and has
been chemically identified as his(2,2,6,6-tetramethyl-4-piperidyl) sebacate.
This compound (25 nmol) blocked 1,4-dihydropyridine-sensitive 45Ca2+ uptake
into GH3 cells with an IC50 value of 3.6 µ M, inhibited Sr2+ currents
through L-type Ca2+ channels in A7r5 smooth-muscle cells in whole-cell
patchclamp experiments after extracellular application, and affected the
high-affinity binding of Ca2+ entry-blocker ligands to a variety of
preparations. Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is a highly
potent (IC50 values <10 nM) inhibitor at the phenylalkylamine- and
benzothiazepine-selective drug-binding domains of the 1 subunit at the
drug-binding domains selective for (+)-tetrandrine or (+)-cis-diltiazem.
This compound is identical to Tinuvin 770, which is used worldwide as a
light stabilizer for polyolefins.
6. X. Michael Liu,* E. Peter Maziarz, Frank Price, David J. Heiler and
George L. Grobe, III (2001) Characterization of silicone rubber
extracts using gel-permeation chromatography, matrix-assisted laser
desorption/ionization mass spectrometry, electrospray ionization mass
spectrometry, Fourier transform infrared spectroscopy and gas
chromatography/mass spectrometry. Eur. J. Mass Spectrom. 7, 473 -
480 (2001)
Abstract:
Extracts from a silicone rubber product were characterized by gel-permeation
chromatography (GPC), matrix-assisted laser desorption/ionization
time-of-flight (MALDI-ToF) mass spectrometry, Fourier transform infrared
spectroscopy (FT-IR), electrospray time-of-flight (ESI-ToF) mass
spectrometry and gas chromatography/mass spectrometry (GC/MS). The extracted
sample was determined to be a complex mixture with a molecular weight
ranging from 200 to 210,000 Da as determined from GPC measurements. Two
additives known as bis(2-ethylhexyl) adipate and bis(2-ethylhexyl) phthalate
were observed in the extract.
7. Kawamura Y, Nakajima A, Mutsuga M, Yamada T, Maitani T.
Residual chemicals in silicone rubber products for food contact use. Shokuhin Eiseigaku Zasshi.
2001 Oct;42(5):316-21. [Article in Japanese]
The residues of additives and other chemicals in 23 kinds of silicone rubber
products for food contact use, including nipples, packing and spatulas,
were investigated by GC/MS. The packing and spatulas contained 80-480
micrograms/g of BHT, 60-5,830 micrograms/g of di(2-ethylhexyl) phthalate
(DEHP), and 60-80 micrograms/g of dibutyl phthalate, while the nipples
contained no additives. All of the samples contained 15 to 20 peaks of
polydimethylcyclosiloxanes. Dodecamethylcyclohexasiloxane (D6) to
tetratriacomethylcycloheptadecasiloxane (D17) were confirmed, and other larger
siloxanes up to pentacontamethylcyclopentacosasiloxane (D25) were estimated. A
rough estimate of the total cyclosiloxane content was 3,310-14,690
micrograms/g. They might be mainly unreacted materials or by-products, and some
of them might be additives. Based on the migration test, no chemicals were
released into 20% ethanol at 60 degrees C for 30 min, though DEHP and the
polydimethylcyclosiloxanes were released into n-heptane at 25 degrees C for 60
min.
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