Lead Stabilisers Risk Characterisation

The toxic effects of lead and lead compounds are well known and have been thoroughly documented (click to read review on lead toxicology of the International Lead and Zinc Study Group). According to the US Agency for Toxic Substances and Disease Registry, lead is in the second position in the Top 20 Hazardous Substances ATSDR/EPA Priority List for 1999 (www.atsdr.cdc.gov/cxcx3.html).

As a consequence, lead and lead compounds are heavily regulated to control exposure during manufacturing, handling during the compounding, use and disposal of PVC.

No serious cases of poisoning linked to the use of lead stabilisers are known.

Lead Compounds used in Stabilisers

  • Tribasic Lead Sulphate [3 PbO.PbSO4.H2O] or Tetrabasic Lead Sulphate [4 PbO.PbSO4.1/4 H2O] (strong heat stabilisers)
  • Dibasic Lead Phosphite [2 PbO.PbHPO3.1/2 H2O] (Heat and Light Stabiliser)
  • Dibasic Lead Phthalate [2 PbO.PbC6H4(COO)2] (Strong Heat Stabiliser – Cable)
  • Polybasic Lead Fumarate (Very strong heat stabiliser – Cable)
  • Dibasic Lead Stearate [2 PbO.Pb(C17H35COO)2] or normal Lead Stearate [Pb(C17H35COO)2] (Stabiliser/Lubricant)

Co-stabilisers such as phenolic antioxidants and lubricants such as paraffins, polyethylene waxes or ester waxes can be used.

Water Solubility and Oral Toxicity of Lead Stabilisers

Stabiliser Solubility (note 1)
% lead in water		 Toxicity (note 2)
LD50 (oral, rat)
Tribasic Lead Sulphate <0.001 > 2,500 mg/kg
Dibasic Lead Phosphite <0.001 >6,000 mg/kg
Lead Distearate 0.002 >2,000 mg/kg

Note 1: according to ISO 787/8
Note 2: Sodium Chloride (common salt) LD50 (oral, rat) = 3,000 mg/kg

From these data it can be seen that PVC lead stabilisers have low acute toxicity.

Labelling and Classification

Lead compounds are listed in Annex I of the Dangerous Substances Directive (67/548/EEC) and must be classified and labelled accordingly (click here for the EU Classification and Labelling of "Lead Compounds, Other"). The manufacturer must supply safety data sheets to industrial users to enable them to take the necessary precautions. Formulated lead compounds are subject to similar legislation as specified in the Dangerous Preparations Directive (88/379/EEC).

Manufacturing and Use of Lead PVC Stabilisers

The principal hazard is exposure and ingestion of dust. There is a trend towards "dust-free" or "one-pack" formulations combining the stabiliser with lubricants and other additives where appropriate to give a low or a non-dusting product.

As a result of their hazardous nature, manufacturers must comply to strict workplace regulations to minimise exposure. Use of substances or preparations that are classified as dangerous is subject to a documented risk assessment ensuring that adequate exposure control measures are taken. Industrial hygienists audit the workplace and measure the amount of airborne dust that can potentially be ingested by workers.

The current EU maximum exposure concentration of lead compounds in air is 0.15 mg/m3. As a further precaution, occupational physicians monitor exposure with biological samples. The maximum level of lead allowed by the EU in blood is 70 µg/dl for men and 40 µg/dl for women. Some countries operate at the level of 40 µg/dl blood for men and 20 µg/dl for women.

In the event that lead levels in air or in the biological samples exceed the limits, further measures can be taken, or the worker might be given an alternative assignment to lessen the exposure. In general, exposure is controlled by modification of the equipment, implementation of adequate ventilation, wearing of personal protection equipment such as dust masks, clothes and gloves, workplace cleaning and observance of high personal hygiene standards.

Manufacturing and Use of the PVC Article Containing Lead Stabilisers

Once the lead stabiliser is incorporated into the PVC matrix, it is no longer bioavailable. The compounded PVC can be shipped in granular form to processors which will mould, extrude or otherwise manufacture the part in its final shape. Finally, the parts themselves can be assembled into the final article such as a window frame. During these steps little or no dust is generated so that generally exposure is not a concern.

The typical lead metal content in major applications is:

  • Pipe 0.75%
  • Window Profile 2.7%
  • Wire and Cable 2.0%

Exposure from processed PVC

Lead stabilisers are locked into the plastic matrix:

  • lead contained in PVC does not migrate from the plastic
  • lead contained in PVC cannot be removed
  • leachability of lead is extremely low

The inertness of lead-stabilised PVC can be demonstrated by extraction studies. For instance, several studies have shown that the amount of lead extracted from lead-stabilised water pipes is negligible when tested according to the requirements of the EU Ceramics Directive (84/500/EEC) which specify the maximum amount of lead that can be extracted from ceramics in contact with food.

The test consists of contacting the pipe sample twice with acetic acid (vinegar). The first test removes the surface lead from manufacture, and the second test shows that there is no migration from the bulk of the PVC:

First Test 0.13 and 0.20 mg/dm2 Lead

Second Test < 0.01 mg/dm2 Lead.

(Source: J.W.A. Averink, paper 3.4 EURAU Seminar in Vienna 1994, cited by I. Björklund, Nordic Pipes Federation)

The Austrian Plastics Industry in two reports has looked at several installed PVC pipe systems and has found that the lead content of the water in the system is no greater than the natural lead content of the water entering the PVC pipe system (Ch. Hametner, B. Hanauser, Osterreichisches Kunstoffinstitut, Vienna, July 1995, Lead Migration from PVC Water Pipes, Pa. Nr. 33.486 and M.E. Novak, Osterreichisches Kunstoffinstitut, Vienna, March 1990, Comment on the Migration of Lead out of PVC Potable Water and PVC Sewage Pipes).

In Sweden, the Nordic Pipes Federation estimated that human exposure to lead from PVC pipes is 0.001 kg/year in regard to the whole Swedish population. This should be compared to the limit imposed by Swedish regulations: 55 kg/year.

For certain uses such as toys and medical packaging, there are specific regulations that are in place to ensure that such products are safe.

In conclusion, the risk of diffused losses to the environment or of consumer exposure is minimised by the encapsulation effect of the PVC that immobilises the lead stabiliser and prevents it from harming man or the environment.

Additional Information on Lead Stabilisers