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Tin
PVC Stabilisers Risk Characterisation
This section
contains excerpts from the Organotin Environmental Programme of
ORTEPA: "Organotin Stabilisers for PVC, a review of applications,
toxicology and ecotoxicology, 2/1997". For more information
on ORTEPA and on tin PVC stabilisers, click on www.ortepa.org/.
The toxicity
of tin compounds to human health and the environment is strongly
dependent of the chemical composition of the compound under study.
Tin metal
in itself has low toxicity. Its use as an internal lining in food
cans is well accepted.
Tin
Compounds used as PVC Stabilisers
The mono-
and dialkyl tin compounds that are used to stabilise PVC belong
to the following families:
RSnX3
and R2SnX2
Where the
alkyl group R can be:
- Methyl,
Butyl, Octyl or Dodecyl
And where
the ligand X can be:
- Mercaptoester
(e.g., thioglycolate), Carboxylate (e.g., maleate), Sulfide
The most common
stabilizers are produced by reaction of mono- and di-alkyltinchlorides
with mercaptoesters.
Classification
and labelling of Tin PVC Stabilisers
Mono- and
dialkyl tin compounds are not listed in Annex I of the Dangerous
Substances Directive (67/548/EEC). In principle, they do not have
to be labelled with specific symbols or carry risk and safety
phrases. However, manufacturers are obligated to review existing
literature and data about their products and classify them accordingly.
As with any other industrial chemical, tin compounds must be handled
by adequately trained workers under supervision.
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Acute
Oral Toxicity Data (LD50, mg/kg body weight)
|
| Compound |
Chlorides
(X = Cl) |
Thioglycolates
(X = SCH2COOC8H17) |
| Me3SnX |
9.2 |
20.4 |
| Bu3SnX |
349 |
1,350 |
| Oct3SnX |
29,200 |
26,550 |
| Me2SnX2 |
74 |
1,210 |
| Bu2SnX2 |
126 |
510 |
| Oct2SnX2 |
7,000 |
1,975 |
| MeSnX3 |
1,370 |
920 |
| BuSnX3 |
2,300 |
1,063 |
| OctSnX3 |
3,800 |
3,400 |
| Source:
Luiten, Klimmer, ITRI Publ. N° 501D |
Due to low
aqueous solubilities, a high affinity to soil and organic sediments
and rapid conversion to inorganic tin in water, the potential
of mono and dialkyl tin compounds for ecotoxic effects is low.
Unfortunately,
the toxicity of mono- and dialkyl tin compounds is sometimes confused
with the toxicity of trialkyl tin compounds to aquatic life. The
primary use of trialkyl tin compounds is as biocidal additives
in marine anti-fouling coatings, and not as stabilisers.
Manufacturing
of Tin PVC Stabilisers
The mono-
and dialkyl tin compounds are produced in chemical plants which
by nature are subject to tight regulations concerning emission
controls and industrial hygiene.
Manufacturing
of the PVC Article Containing Tin Stabilisers
- 8-hour
Threshold Limit Value (TLV): 0.1 mg/m3 as tin
- Short Term
Exposure Level (TLV-STEL): 0.2 mg/m3 as tin
(sources:
ACGIH, MAK Commission)
Several studies
have concluded that all organotin compounds can be safely handled
during PVC processing (www.ortepa.org/stabilisers/pages/humanhealthaspects.htm)
Use
of the PVC Article Containing Tin Stabilisers
Migration
data from PVC food wrap containing tin stabilisers show that the
migration levels of tin are well within limits (TNO Nutrition
and Food Research – Determination of the overall and specific
migration from an A4-film – Project N° 815532 –
Analytical report N° 1-5 – June 1995).
Migration
Limit Values
Food Packaging:
- 0.005 mg
tin/dm2 with water-based simulant
- 0.01 mg
tin/dm2 with fat simulant
Potable Water
Pipe: 0.05 mg tin/l
Organotin
stabilisers have wide national approvals for food contact applications.
The Tolerable Daily Intakes of mono- and dialkyl tin compounds
have been set at:
- Mono octyl
tin compounds 0.02 mg/kg body weight
- Di octyl
tin compounds 0.0006 mg/kg body weight
- Mono and
di methyl tin compounds 0.003 mg/kg body weight
(source: European
Commission, Reports of the Scientific Committee for Food (thirty-third
series), 1995, ISBN 92-826-9275-2)
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