Epoxy Resin Can Coatings and Bisphenol A Safety Information
Summary
The Can Coating Migration Study
Results
Conclusions
References
 Summary
Metal food and beverage cans have a thin coating on
the interior surface, which is essential to prevent
corrosion of the can and contamination of food and beverages
with dissolved metals (UK
FSA, 2002). In addition, the coating helps to prevent
canned foods from becoming tainted or spoiled by bacterial
contamination. The major types of interior can coating
are made from epoxy resins, which have achieved wide
acceptance for use as protective coatings because of
their exceptional combination of toughness, adhesion,
formability and chemical resistance. Such coatings are
essentially inert and have been used safely for over
40 years. In addition to protecting contents from spoilage,
these coatings make it possible for food products to
maintain their quality and taste, while extending shelf
life.
Bisphenol A (BPA) is a key building block of epoxy
resins. In 1995, Brotons and coworkers reported that
BPA could migrate from can coatings during the food
canning process. Later that same year, the Society of
the Plastics Industry, Inc. (SPI), initiated a study
to quantify the migration of BPA from can coatings.
Based on the results of the SPI study, the estimated
dietary intake of BPA from can coatings is less than
0.00011 milligrams per kilogram body weight per day.
This level is more than 450 times lower than the maximum
acceptable or “reference” dose for BPA of
0.05 milligrams per kilogram body weight per day established
by the U.S. Environmental Protection Agency.
Stated another way, an average adult consumer would
have to ingest more than 230 kilograms (or about 500
pounds) of canned food and beverages every day for an
entire lifetime to exceed the safe level of BPA set
by the U.S. Environmental Protection Agency.
In 2002, the safety of epoxy resin can coatings was
confirmed by an analysis of the European Commission’s
Scientific Committee on Food (SCF). The SCF estimated
total dietary intake of BPA from all food contact sources,
including epoxy resin coatings, to be in the range of
0.00048 to 0.0016 milligrams per kilogram body weight
per day, which is below the Tolerable Daily Intake set
by the SCF of 0.01 milligrams per kilogram body weight
per day.
Consequently, the potential human exposure to BPA
from can coatings is minimal and poses no known risk
to human health. Can coatings have been and continue
to be recognized as safe by the U.S. Food and Drug Administration,
the U.K. Food Standards Agency, the EU Scientific Committee
on Food and other government bodies worldwide.
The
Can Coating Migration Study
- In 1995, after Brotons and coworkers reported migration
of BPA from can coatings during food canning (Brotons
et al, 1995), the Society of the Plastics Industry,
Inc. (SPI) initiated a study of BPA migration from
can coatings (Howe et al, 1998). In the first phase
of this study, the analytical signal was noted to
have an unusual or unsymmetrical shape, suggesting
that not all of the material detected was really BPA.
- To follow up on the results of the first phase,
nine laboratories conducted a series of tests to compare
analytical methods for detecting BPA. The analytical
methods tested included high performance liquid chromotography
(HPLC) and gas chromotography with mass spectroscopy
(GC/MS). The results of this second phase confirmed
the presence of interfering materials (unidentified
substances) that could be mistaken for BPA.
- Two additional series of tests were conducted to
identify the HPLC and GC/MS methods that best eliminated
the interfering materials and to ensure that these
methods could be reliably conducted in an independent
laboratory (Wingender et al, 1998).
- Using the preferred analytical methodology, fourteen
can samples, representing food cans produced by the
major American can manufacturers and their coating
suppliers, were tested. Nine of the samples were identical
to those examined in the initial phase of this study.
All cans contained maximum levels of coating formulations
using epoxy resin systems.
- Detection of BPA migration was enhanced by using
easily analyzed food simulating solvents rather than
actual foods – either 10% ethyl alcohol to simulate
water-based foods, such as fruit juice, infant formula,
and other beverages, or 95% ethyl alcohol to simulate
fatty foods, such as meats and other canned foods.
- Storage conditions for sample cans containing the
food simulating solvents were those prescribed by
the U.S. Food and Drug Administration (FDA,
1995, revised 2002) to exaggerate the normal canning
processes used. For “hot- filled” products
such as fruit juice, cans were filled with hot solvent
(10% ethyl alcohol), held at 212° F for 30 minutes
and stored for 10 days at 120° F. For “retorted”
products (all other samples), cans were filled with
the appropriate solvent (10% or 95% ethyl alcohol),
heated under pressure at 250° F for two hours
and then stored for 10 days at 120° F.
- Bisphenol A levels in the food simulating solvents
from the can samples were quantified using the HPLC
and GC/MS analytical methods developed to reliably
detect BPA without interference from other materials
in the solvents. The lowest amount of BPA that can
be detected (the limit of detection) using these procedures
is 5 parts per billion.
Results
- The first phase of the SPI study found no detectable
migration of BPA for the three beverage/beer can coatings
tested with an analytical method sensitive to 5 parts
per billion. Since neither BPA nor interfering materials
that could be mistaken for BPA were detected, these
results are valid and only food cans were included
in the second phase of the study.
- In the second phase of the study, the HPLC and
GC/MS methods gave virtually identical results with
all food can samples, confirming the accuracy and
reliability of the improved analytical methods.
- The measured level of BPA migration in the nine
types of food cans analyzed in the first phase and
again analyzed in the second phase of the stud y dropped
from an average 63 parts per billion (first phase
analytical methods) to an average of 36 parts per
billion (second phase analytical methods). This 43%
decrease in average levels is due entirely to the
use of analytical methods that eliminated interfering
(non-BPA) materials.
- The average level of BPA migration from the full
set of 14 cans analyzed in the second phase of the
study was 37 parts per billion.
- The potential dietary exposure to BPA from canned
foods and beverages can be estimated using procedures
recommended by the U.S. Food and Drug Administration
(FDA,
1995, revised 2002):
dietary concentration = CF x [(fwater-based
x Mwater-based) + (facidic x Macidic) + (flow alcohol
x Mlow alcohol) + (ffatty x Mfatty)]
In this equation, “CF” is the “consumption
factor,” the fraction of the average individual’s
diet that is likely to contact a specific type of
packaging material, such as can coatings. Also in
this equation, “f” is the “food-type
distribution factor”, the fraction of each food
or beverage type that contacts a packaging material,
“M” is the migration value for that type
of food in contact with the packaging material, and
the food types are indicated by the subscript description
(water-based, acidic, low (<15%) alcohol or fatty).
- Estimates of the CF and f values for canned food
and beverages are available from FDA (FDA,
1995, revised 2002). The f- values are estimated
to be 0.16, 0.35, 0.40 and 0.09 for water-based, acidic,
low alcohol and fatty foods. The Mvalue for acidic
and low alcohol foods is the value (< 5 parts per
billion) measured for beverage cans, and the value
for water-based and fatty foods is 37 parts per billion.
With these parameters, the average concentration of
BPA in all canned food and beverages together is <13
parts per billion.
The quantity of food and beverages packaged in polymer-coated
metal cans is estimated at 17%, corresponding to a
CF value of 0.17. Thus, the potential concentration
of BPA in the entire diet from canned foods and beverages
is <2.2 parts per billion.
Assuming, as does FDA, that the average individual
consumes 3000 grams of food and beverages per day,
the potential dietary concentration of <2.2 parts
per billion corresponds to a potential daily intake
of less than 0.0066 milligrams per person per day.
Based on FDA’s estimate that a typical individual
weighs 60 kilograms, the estimated dietary intake
of BPA from can coatings is < 0.00011 milligrams
per kilogram body weight per day.
This level is more than 450 times lower than the maximum
acceptable or “reference” dose for BPA
of 0.05 milligrams per kilogram body weight per day
(EPA,
1993). When the dietary intake of BPA from can
coatings is combined with other sources of dietary
exposure to BPA, the total dietary intake of BPA (<0.00012
milligrams per kilogram body weight per day) from
all sources is still more than 400 times lower than
the reference dose (BPA
INFO, 2002). The reference dose is defined by
EPA as an estimate of a daily oral exposure to the
human population (including sensitive subgroups) that
is likely to be without an appreciable risk of deleterious
effects during a lifetime.
- With an average concentration of BPA in all canned
food and beverages of <13 parts per billion (equal
to <0.013 milligrams BPA per kilogram food/beverage),
an average adult consumer weighing 60 kilograms would
have to consume more than 230 kilograms (or about
500 pounds) of canned food and beverages every day
for an entire lifetime to exceed the reference dose
of 0.05 milligrams per kilogram body weight per day.
- The reference dose for BPA has recently been confirmed
by a three-generation study in rats (Tyl et al, 2002),
which found no adverse effects on reproduction from
BPA at doses of 50 milligrams per kilogram body weight
per day and lower. The US EPA calculated the reference
dose by dividing the Lowest-Observed- Adverse-Effect-Level
(LOAEL, 50 milligrams per kilogram body weight per
day) from an earlier chronic toxicity study by an
uncertainty factor of 1000. Applying that same uncertainty
factor to the No-Observed-Adverse-Effect-Level (NOAEL,
50 milligrams per kilogram body weight per day) from
the Tyl study confirms the safety of the reference
dose, 0.05 milligrams BPA per kilogram body weight
per day. Since the maximum estimate of BPA exposure
from can coatings is over 450-fold lower than the
reference dose, the potential human exposure to BPA
from can coatings is minimal and poses no known risk
to human health.
- In 2001, the UK Food Standards Agenc y (FSA) reported
the results of a survey of BPA content in canned foods
and beverages purchased in the UK (UK FSA 2001; Goodson
et al, 2002). The levels of BPA found in foods and
beverages are generally consistent with the results
reported by SPI (Howe et al, 1998), which were measured
in food simulating solvents. In all but one canned
beverage, BPA was not detected at a limit of detection
of 2 parts per billion, which is below the 5 parts
per billion limit of detection in the SPI study. In
most of the canned food samples, BPA, when detected,
was found at levels comparable to or lower than the
average level of 37 ppb for food cans reported in
the SPI study. For all canned foods and beverages,
the UK FSA estimated an average upper bound BPA level
of 21.7 parts per billion. Using a different methodology
that assumes higher consumption of canned foods and
beverages than the FDA methodology, the UK FSA estimated
a BPA dietary intake of 0.00036 to 0.00038 milligrams
per kilogram body weight per day.
- Based on the UK FSA survey data, the UK Committee
on Toxicity of Chemicals in Food, Consumer Products
and the Environment (COT) assessed the potential health
implications of BPA in canned foods and beverages
(COT,
2001; Goodson et al, 2002). The COT concluded
“that the levels of BPA identified in canned
foods analysed in the FSA survey are unlikely to be
of concern to health, and that there is no reason
for consumers to change their source of foodstuffs
as a result of these findings.”
- The Scientific Committee on Food (SCF), which is
an independent advisory committee to the European
Commission on food safety matters, has recently evaluated
the safety of BPA from all food contact sources including
epoxy resin coatings. The SCF set a Tolerable Daily
Intake (TDI) for BPA of 0.01 milligrams per kilogram
body weight per day after a comprehensive review of
all robust scientific data covering all aspects of
toxicity. Similar to the EPA reference dose, the TDI
represents a lifetime exposure level that is considered
to be safe. Based on the existing migration data,
the total exposure to BPA from all food contact sources
was estimated to be in the range of 0.00048 to 0.0016
milligrams per kilogram body weight per day for adults
and infants respectively, which is below the TDI value
set by the SCF. Similar to the UK FSA analysis, the
methodology used by the SCF assumes higher consumption
of canned foods and beverages than the FDA methodology.
This assessment also confirms that epoxy resin coatings
for food and beverage cans are safe for use and pose
no known risk to human health (SCF,
2002).
Conclusions
- Epoxy resins provide an important coating for food
and beverage cans that helps to protect food and beverages
from contamination with dissolved metals and from
spoilage due to bacterial contamination. Can coatings
are essential to maintaining the quality and integrity
of canned food and beverages.
- Human exposure to BPA from can coatings is minimal
and poses no known risk to human health. Can coatings
have been and continue to be recognized as safe by
the U.S. Food and Drug Administration, the U.K. Food
Standards Agency, the EC Scientific Committee on Food
and other government bodies worldwide.
- Care must be taken in selecting an analytical method
for measuring the migration of BPA from can coatings.
Other materials in food or beverages may interfere
with the accurate measurement of BPA, leading to overestimation
of igration values.
- Using appropriate analytical methods, no BPA was
detected from beverage/beer cans with a limit of detection
of 5 parts per billion. Bisphenol A migration levels
from food cans averages 37 parts per billion.
- Using FDA recommended values and procedures, which
exaggerate canning and storage conditions, the potential
dietary intake of BPA from food and beverage cans
is less than 2.2 parts per billion and the estimated
dietary intake is less than 0.00011 milligrams per
kilogram body weight per day. The estimated daily
intake of BPA from canned food and beverages is over
450 times lower than the maximum acceptable or reference
dose for BPA of 0.05 milligrams per kilogram body
weight per day.
- The UK FSA and COT have confirmed that the levels
of BPA in canned foods are unlikely to be of health
concern. The SCF has also confirmed that exposure
to BPA from all food contact sources, including epoxy
resin food and beverage can coatings, is below the
Tolerable Daily Intake and therefore is safe.
References
BPA INFO (Bisphenol A: Information Sheet), 2002, “Human
Safety: An Overview.”
Brotons, J.A., M.F. Olea-Serrano, M. Villalobos, V.
Pedraza and N. Olea, 1995, Environmental Health
Perspectives, vol. 103, pages 608-612.
COT (Committee on Toxicity of Chemicals in Food, Consumer
Products and the Environment), 2001, “Statement
on a Survey of Bisphenols in Canned Foods”, April
2001. Available on the Internet at
http://www.food.gov.uk/multimedia/pdfs/bisphenols.pdf
EPA (U.S. Environmental Protection Agency), Bisphenol
A, CASRN 80-05-7, IRIS, Integrated Risk Information
System, on-line, 1993. Available on the Internet at
http://www.epa.gov/iriswebp/iris/subst/0356.htm
Howe, S.R., L. Borodinsky and R.S. Lyon, 1998, “Potential
Exposure to Bisphenol A from Food-Contact Use of Epoxy
Can Coatings,” Journal of Coatings Technology,
vol. 70, no. 877, pages 69-74.
FDA (U.S. Food and Drug Administration), 2002, “Preparation
of Food Contact Notifications and Food Additive Petitions
for Food Contact Substances: Chemistry Recommendations,”
Center for Food Safety and Applied Nutrition, Office
of Food Additive Safety, FDA, Washington, D.C., April
2002. Available on the Internet at http://www.cfsan.fda.gov/~dms/opa2pmnc.html
Goodson, A., W. Summerfield and I. Cooper, 2002, “Survey
of bisphenol A and bisphenol F in canned foods,”
Food Additives and Contaminants, vol. 19, pages
796-802.
SCF, 2002, “Opinion of the Scientific Committee
on Food on Bisphenol A”, April 17. Available on
the Internet at
http://europa.eu.int/comm/food/fs/sc/scf/out128_en.pdf
Tyl, R. W., C. B. Myers, M. C. Marr, B. F. Thomas,
A. R. Keimowitz, D. R. Brine, M. M. Veselica, P. A.
Fail, T. Y. Chang, J. C. Seely, R. L. Joiner, J. H.
Butala, S. S. Dimond, S. Z. Cagen, R. N. Shiotsuka,
G. D. Stropp and J. M.Waechter, 2002, “Three-Generation
Reproductive Toxicity Study of Dietary Bisphenol A in
CD Sprague-Dawley Rats,” Toxicological Sciences,
vol. 68, pages 121-146.
UK FSA (United Kingdom Food Standards Agency), 2001,
“Survey of Bisphenols in Canned Foods”,
March 2001. Available on the Internet at
http://www.food.gov.uk/science/surveillance/fsis-2001/bisphenols
UK FSA (United Kingdom Food Standards Agency), 2002,
“Food Safety Information Sheet: Tin in Canned
Fruits and Vegetables”, August 2002. Available
on the Internet at
http://www.food.gov.uk/science/surveillance/fsis-2002/tinincannedfruitandveg
Wingender, R.J., P. Niketas and C.K. Switala, 1998,
“Development of Methods for the Determination
of Bisphenol A in Food Simulants,” Journal
of Coatings Technology, vol. 70, no. 877, pages
75-82.
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