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PVC Home Page
Summary & conclusions
Phthalate Plasticizers
July, 2002: Recent questions from our email inbox
Also -interview with a vinyl industry spokesperson. Read our comments!
Easy-to-print version of this report
(26 sec @ 28k)
Other hazards
References
Authorship of this material
Most recent list of toys
made with PVC (March 1999)
Update, Jan. '99:
Lead, Cadmium, Phthalates still found in Children's
Products
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Polyvinyl Chloride is a polymer,
or large chain-like molecule, made up of repeating units of Vinyl Chloride
(a monomer). Commonly referred to as Vinyl
or PVC, it is exceeded only by polypropylene and
polyethylene in the variety of products which are made from it.
Other common commercial polymers used for familiar products are
polyurethane and polystyrene.
We find PVC in car interiors
and trim, wall coverings, floor tiles, window frames, siding, water and
sewer pipes, shrink wrap, packaging (including blister packs and food
wraps), medical equipment (tubing, transfusion bags, blood
storage bags, respiration tubes), electric and electronic cable
insulation, textiles, both as trim and complete garments - and Toys.
PVC can be a tough, rigid material, or soft and flexible,
depending on the use of additives. It is denser than other
plastics, and so preferred by food processors for packaging.
Additives include anti-oxidants (heat and light stabilizers)
to extend the life of the plastic, and plasticizers to
allow a precise degree of flexibility.
All polymers, in a perfectly pure state, at room temperature,
are completely non-toxic, since they are nearly inert and
insoluble. However, all commercial polymers require a variety of additives.
They all undergo degradation and decomposition when exposed to
heat during formulation or molding into products. They also tend
to break down when subject to the mechanical stress of molding or
extrusion.
Finally, all products made from polymers are degraded
by the light, heat, stress, and air pollution encountered in everyday
use. For this reason, one or more stabilizers
are required for each type of plastic.
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Stabilizers in
PVC: PVC has the special problem of forming HCl
(Hydrochloric Acid) when it degrades, which causes a chain reaction which
proceeds rapidly to complete loss of strength (and causes damage to
manufacturing equipment). The stabilizers for PVC have thus mostly
been metal salts, which could react with the HCl. These have included
Lead, Cadmium, Barium, Calcium, Zinc, and organic Tin compounds. (July 2000: Organotin compounds found to
interfere with immune system cell activity.)
Organotins, principally dibutyltin and monobutyltin, are used as stabilizers in
Vinyl as an alternative to Lead and Cadmium. Their principal use is in
clear vinyl products.The first
two are known poisons. It appears that Cadmium is not much used any more.
There are varying accounts in the literature we have seen concerning the
prevalence of Lead as a stabilizer. According to an Australian document
dated 1996, it is still quite widely used.
Lead is not used where a clear Vinyl is required. Window covering, food packages, tubing, etc, use Organic Tin Compounds
(Organotins) or Calcium/Zinc. There have been some findings linking
Organotins to Reproductive and immune system problems. A compound
similar to ones used in PVC is used in marine antifouling paint, and has been
blamed for destruction of marine life in harbours. Australia has
banned the use of of this Organotin.
Stabilizers are not chemically bound to the
PVC polymer chains. Only the amount of stabilizers which
reacts with damaged parts of the polymer become chemically bound. Whether mixed in during formulation, or into the melt during manufacturing,
stabilizer molecules are held in place when the melt freezes, like objects in
an ice cube. Heat Stabilizers are typically added at the rate of
about .5 percent (.005) of the polymer. Metal salts (like lead
carbonate, etc) don't "like" to be mixed into an organic polymer,
and so tend to clump and migrate when the polymer is heated, or in surface
areas subject to weathering and stress. For this reason, we expect the
stabilizer to accumulate on the surface in normal use, especially if the
product is exposed to heat, stress, or light, particularly direct
sunlight. Smith (1996) cites the leaching of lead from new PVC pipe.
Availability of Lead in Toys: In
1995, the Arizona Department of Health Services, responding to the lead poisoning of
children in situations where no obvious source existed, found the source to be rigid Vinyl
miniblinds in the children's rooms. There were very large amounts of lead dust on
the PVC blinds, as well as lead dust on the windowsills below. Two of the children had
been chewing on the blinds themselves. At first, the CPSC declined to identify the
blinds as a hazard, but in June 1996 they agreed to do so. Subsequently,
sampling in North Carolina found miniblinds to be a lead hazard, with surface lead dust
exceeding federal standards by as much as 100-fold. No formal recall was ever
issued, despite vigorous urgings by the authorities of both states. The Window
Covering Safety Council, throughout all this, put out press releases reassuring consumers
that the lead found in the blinds did not constitute a hazard to children.
Motivated by this finding, Greenpeace collected some popular mass-market PVC toys,
and contracted with two independent laboratories to test for the presence of lead.
In short, they found that about 20 percent of the toys tested contained Lead,
Cadmium, or both. In many of the toys, the levels were high enough to exceed federal
guidelines. They repeated this process in several major U.S. urban areas, with
similar results. Their complete report is provided on this website (from link in
section below). The CPSC performed a small-scale replication of the study.
They obtained roughly similar results, but concluded that the lead found on the surface of
the tested toys did not constitute a health hazard to children. Their conclusion was
based on assumptions, definitions, and interpretations, rather than substantially
different quantitative findings.
CPSC concluded that Greenpeace mis-interpreted its own results, by making errors in basic
science, and wrong assumptions about children's behavior. They concluded the products
tested, even ones containing Lead, were not hazardous to children, because the daily
dosage of poisons ingested were below hazardous levels. Health Canada performed a similar
evaluation, with identical conclusions and interpretation. Environ
Corporation, a think-tank hired by the Vinyl Industry Association, offered similar
"findings", although did no actual laboratory work. These reports are also
posted on this website (see "links" below).
CPSC, Environ, and Health Canada, criticized the Greenpeace study
principally on four grounds:
1. Accelerated aging tests using exposure to ultraviolet light were
not valid, because the toys tested by Greenpeace would not be exposed to ultraviolet
radiation in normal use, unlike the miniblinds in the sunny windows.
2. Great variations in city-to-city lead measurements, and variations
from the CPSC results for the same toy indicates defects in Greenpeace's laboratory
procedures.
3. A criticism of the Greenpeace study is inherent in CPSC's decision not
to test the lead content of the electronic cables tested by Greenpeace, on the basis that
children would not be expected to handle this material.
4. Estimates of amounts of lead a child would ingest by handling these
toys were in error, since a child would not handle the entire object at once. Thus, amount
of lead dust per unit area are a more correct measure than total dust on surface of item.
Assuming certain values for a child's hand size, amount of daily handling,
and correlations of blood levels with amounts ingested, the critics concluded that the
resulting blood lead levels would remain below established Federal standard of
10µg/dl.
Responding to the first comment:
The critics are incorrect on a point of basic scientific information, and deficient in
simple observations of child behavior and demographics. The miniblinds were exposed
to light transmitted through glass, as well as the resulting heat. "Glass in
general is opaque to the ultraviolet and infrared". (Physics and Chemistry Handbook,
1964 edition ). Carbon-carbon and carbon-hydrogen bonds are broken far more
readily by shorter than by longer wavelengths. Any toy likely to be played with
outdoors, or inadvertently left outside, would receive far more short wavelength
ultraviolet light, available only in direct sunlight. A number of the toys
analyzed by Greenpeace are in that category; some might even be used as beach toys.
In a large sub-tropical metropolis like Los Angeles or Miami,
the
rapid disintegration of sun-exposed PVC, as well as rubber and other polymers,
is a
familiar problem.
Responding to the second comment: The analysis was not
performed by Greenpeace, but by two accredited and professionally staffed labs,
specializing in lead analysis. The variations in percent lead content are far more likeley
due to poor quality control at the manufacturing plants which processed the PVC resin. The
very highest numbers, well over the theoretically useful quantities for metal salt
stabilizers, are probably just due to gross over-use of the additives, which is something
that would occur on a random basis.
Responding to the omission of testing of cable insulation: It is
not productive to make such assumptions about children's behavior. Children can, and
eventually will, handle everything in their daily surroundings. We have an article
from Centers for Disease Control reporting the severe lead poisoning of adult
electronics worker who had developed the habit of chewing on lead-stabilized
PVC electric insulation. Lead hazard is thus not just a problem for children; but
the point is that children are especially at risk, due to their unpredictable behavior and
greater sensitivity to the toxic effects of lead.
Responding to the fourth criticism, we consider the
toxicology of Lead: In short, the daily intake of lead is not as
important a determinant of ultimate harm as is the duration of exposure and the total lead
ingested over time. This is due to the cumulative nature of lead toxicity.
Lead at very low blood levels causes a very wide variety of changes in neural
functioning. It interferes with transmission of nerve signals both by disruption of
Calcium ion balance along the nerve axon, and at the synapse, by bonding to Calcium
receptor sites. Lead can modify gene expression and gene-regulated
protein synthesis. Lead exposure interferes in a variety of ways with the developing
brain at the neuroanatomical level. Prolonged exposure to low levels of lead changes
the response of various neurotransmitter systems. Consistent and reproducible
behavioral effects have been seen with blood lead levels as low as 7 µg/dl (micrograms of
lead per tenth liter of blood), which is below the Federal standard of 10
µg/dl.
The CPSC suggests in its report that "chronic ingestion of lead be limited to
15µg per day" to prevent children of 6 years and younger from exceeding the 10
µg/dl blood lead level. It is not clear from the CPSC report how the daily
ingestion rate translates to the suggested maximum blood level.
In any case, there is good reason to assert that the daily intake of lead for a child is
not relevant to a discussion of the hazards of the material. Lead is a uniquely
cumulative poison. Some of the kinds of neurological damage caused by lead are not
reversible. The period from 1 to 3 years of age in humans is critical for lead
exposure, and neural damage occuring during this period is least likely to be
reversible.
Most important, children excrete lead very slowly. Lead behaves chemically
very much like Calcium, and is similarly stored in bone. Bone is in a dynamic
equilibrium, biologically and chemically, with blood. If the rate of lead intake is
reduced, lead will enter blood from bone. Thus, a daily exposure, however low,
builds up a "savings account" of lead, which may persist for decades.
During periods of high calcium demand, as in lactation and pregnancy, lead enters the
blood along with the calcium. In older people, when bone mass is reduced by
resorption, higher lead levels have been observed. This is especially true of
post-menopausal women, who are greater risk of osteoporosis. (It thus seems that
female children are at particular risk from lead ingestion.)
It is also important to be aware that the lead available from the tested products would
not be the only source of exposure in a child's environment. Although substantial
and very successful efforts have been made in the past twenty years to reduce
environmental lead (removal of lead paint and banning its use in most applications, the
elimination of leaded gasoline and lead plumbing solder), there are still other sources of
lead exposure. Due to the years of environmental accumulation, children are still
exposed to other sources of lead beside toys. Since all lead exposure is additive as
well as cumulative, it is important to eliminate any source of exposure when it is within
our power to do so.
For these reasons, we feel it is reasonable to assert that the series of calculations
presented by CPSC to arrive at the conclusion that the lead found in some toys is not a
hazard, is not helpful in ensuring safety for children.
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