Document YDkbxnaDbK94XQXNmEXVvakDK

' ('Notes to Industry No.11.) Lead in Paint j i ! i i TECHNICAL INFORMATION SERVICES JAN 2 C 188? GLIDDEN-DURKEc STRONGSVILLE, OrO a oAj l / - ~r&y,tci rBunt RESEARCH ASSOCIATION h 4 CLD Ol 79 (>4 When compared with modern paints, the pre-war white lead based measured as total lead in the dry paint film. As expected the v OomponanU of Paint A* mjj'irn decorative paint, at purchased Irom the local DlY supplier or supermarket is made from three major components: Solvent Binder Ptgmeni The solvent is a volatile liquid the purpose ol which it to reduce the viscosity of the liquid paint sufficiently to assist application by brush or roller. The binder is a polymeric resin, a plastic type material which serves to form a thin coherent film when the solvent evaporates. Th# pigment is a linely powdored opaque material which is in soluble in the solvent and whose functions include colouring the paint and improving its hiding power. Strictly speaking pigments have refractive Index greater than about 1-7. Powdered materials with lower relraetive indices, when incorporated into paints, are known as extenders. In addition to these three major components almost all paints contain small amounts of additional materials (known as additives) which perform certain specific functions not fulfilled by the major ingredients. One of the most important additives in decorative paints are the driers. These are metal compounds without which the drying time of a conventional white spirit based decorative paint would be measured in days rather than in hours. Formulations of Paint Two main types of decorative paints are available today; those based on the solvent while spirit and those based on water. In a white spirit based paint the binder is dissolved In the solvent. Wtsen the paint is applied, the white spirit evaporates to leave a sticky dispersion of pigment in binder which, over a period of several hours, reacts with oxygen in the atmosphere to form a dry lilm. It it this reaction with oxygen which is speeded up by the metal driers. The water-borne paints differ in that the binder is not dissolved in the water but is dispersed in the form of an emulsion. When these "emulsion paints" are applied, the water evaporates and the small particles of binder coalesce to form a coherent dry film. Ihere is no reaction with atmospheric oxygen and hence no need for the presence of driers. Any lead In a decorative paint will originate primarily Irom the pigments and addilivtfs and those concerned with the toxic hazard of lead must take into account the fact that paint formulations have changed markedly over the years. In older buildings it is quite possible that the original paint was never completely removed but was simply overcoated. Pre 1930 paint films are liable to contain substantial amounts of white lead, a basic carbonate of lead approximating 10 2PbC03 Pb (OH)2 Basic sulphnte white lead; PbO x PbS04 (x is between 2 and 6) was alfo used but in much smaller amounts Coloured lead pigments included Chrome yellow Red lead Chrome green Brunswick green (PbCrO<4 - PbS04l (PbaCM + PbO) (Chrome yellow + iron blue) (Chrome yellow + iron blue * barytes). These pigments were used with a linseed oil binder thinned with turpentine for application to woo<J or metal. Water-based coatings intended lor use on interior walls and ceilings were also manu factured. The simplest of these was whitewash, a disjwrsion ol lime in water to which a little tallow might be added as a binder. Alternatively whiting was dispersed in an aqueous solution of glue or casein to form distempers, bead is unlikely to be found in while ceiling coatings of this period but will probably be preseni in coloured wall paints. It should be remembered that lead is not the only toxic element likely to be found in paints; arsenic based pigments were also used In paints made before the turn of the century. Between the wars the higher cost of lead-based pigments tended to limit ttveir use to high quality paints. In fact it was a matter of pride to decorators to advertise that they used "only genuine white lead paints". Many people remember the long-lasting properties of paints in the 'twenties and 'thirties and tend to associate them entirely with the use of lead pigments. In truth they should also take into account factors such as the much higher quality of timber then available and Iso the higher stendard of craftsmanship of carpenters and painters. Old and Modern When compared with modern paints, the pre-war white lead based coatings has several disadvantages (discounting cost and toxicity). They only gave,at best, a semi-gloss finish and one which, unless applied by a skilled craftsman, was very prone to show brushmarks. The drying time was much longer and the paints also tended to darken dun to reaction of the pigment with atmospheric pollution. However, the association. in people's minds between lead paints and quality still lingers; Until recently the.tiLC specified the use of feed primers and it is not uncommon for leases to contain a clause stating that the property should be repainted periodically using a lead based paint. During the Thirties low quality grades of titanium dioxide pigments began to be used end their properties were enhanced by tha use of antimony oxide pigments. Good quality antimony oxide is virtually insoluble, end therefore non-toxic, but it is possible that some of these paints may contain detectable amounts of soluble antimony and possibly arsenic as an impurity. The lead content of water-borne coatings applied during this period is unlikely to differ significantly from that of pre 1930 paints although Ihe higher cost of lead pigments and lire increasing availability of synthetic substitutes both tended to favour a lower lead content for coloured wall paints. After 1945 the availability ol high quality grades of the white pigment titanium dioxide, coupled with the escalating price ol lead, tonded to limit the use of lead pigments to wood end mete) primers. Synthetic resins in white tpirit based air-drying for/m/l'lioni were used, invariably in conjunction with lead driers, but tha lead content of these would not account for more than 1 per cent of tha total dry film. Galvanised steel window frames, manufactured from the fifties on wards, wore often coated with primers based on calcium plumbate 2 CaO - Pb02. These hlgh-lead primers can present a special harerd because they tend to Hake off on ageing. Untreated steel winriowfrantui might well be coated with another high lead prime/ based on red lead. tied Content Control With increasing awareness of the harardi of lead it was considered that more stringent controls should be placed on tho lead content of paints available to the general public. Accordingly, in 1963, an agreement was reached between tha Ministry of Health and the Peintmekeri Association of Great Britain by which the manu facturers undertook that they would label any paint containing mora than one per cent of lead in the dry film or containing any known toxic compound! of other metal*. This label slates: Caution Do not apply on toys, furniture or interior surfaces which might be chowed by children. In practice, the effect of this voluntary agreement is that almost all decorative paints are now formulated so at not to require the cautionary labelling. The lead content of modern decorative paints now tends to be less than 0 6 per cent ahd some ranges contain less than 0.1 per cent. According to the Lawther report it is estimated that lead paints now make up less than three per cent of total sales in the UK. Most of this it used in the construction and shipbuilding industries. As long ago as 1972 the Paintimikers Association of Great Britain issued a recommendation to its members to discontinue the production or sale of proprietary lead based printers for wood and, according to the Lawther report IPara. 69), these are no longer being manu factured. This statement is erroneous: the primers are not usually sold by DlV shops or supermarkets but are obtainable from builders merchants. Regulations Until recently the only general legal restrictions on lead paints in the UK were the Lead Paint Regulations 1927, These required lead paints to be labelled as such and imposed restrictions on their use i.e. for interior spraying or dry rubbing down. For the purpose of these regulations a lead paint was defined as one in which the piQment yielded more than five per cent of soluble lead compounds when extracted under specified conditions with hydrochloric acid. These regulations have recently been superseded by tho Control ol Lead at Work Regulations 1980,and the Hoalth and Safety Commission have issued a Code of Practice which gives guidance on (he interpretation of these regulations and also considers protective measures, air and biological monitoring and analysis. The lead content of paints used on children's toys was restricted by the Toys (Safety! Regulations 1974 to 0.25 per cent (2500 ppm} measured as total lead in the dry paint film. As expected the restrictions on lead in paints on pencils etc. are more stringent and Gl0017965 v the-Pencils nxi Graphic Instruments (Salotyl Regulation) 1974 V-n*t fhe amount ol lead to 0.026 per cent (260 ppm). However, tint l_ defined at the soluble lead content of the dry film, i.c. lead which is extractable under specified conditions using hydrochloric acitf.* Thus rurrent UK regulations define the lead content of paints boih in terms ol total and of soluble lead and ihurt arc arguments lor and against both methods of definition. Front the point ol view of lha analyst, total lead is preforable since this value it unambiguous and can be determined precisely and reproducibly by dilferent laboratories. However, medical authorities will argue that the amount of soluble lead is the really important parameter, This poses the problem of how to deline soluble since the quantity of soluble lead which can be extracted from a dried paint depends upon (he composition of the solvent, the sire of the paint panicles, tlie temperature and duration of the extraction stage, the method of dispersing the particles in the solvent and the way in which the insoluble material is separated from the solution. Unless an analytical method defines all these parameters it is very unlikely that it will give good interlaboretory replication. Lawthar Report The Lawtlicr report defines sources of lead peculiar to a local environment o< specific j.uxkict as "adventitious'' and regards lead paints as the most important tingle cause of lead poisoning in children, However, it must be emphasised that this is due to the ingestion of old lead paintwork in the home. The low lead content of modern decorative paints means that it is virtually impossible for a child to ingest sufficient dry paint to cause harm, Children are particularly at risk because of tlieir habit of mouthing, lucking or chewing non-edible objects. The inQeshon of substances not normally regarded as foodstufls is defined as "pica" and its occurrence in children has been the subject of extensive medical research over the past lew decades. Pica in children has been correlated with ethnic origin, iron deficiency, disturbed motherchild relationships, a tendency towards addiction and a low mental age. However, ail research of this type is complicated by the need for a more precise definition of pice. It is a very rare child that has never pieced toy or other item in its mouth and almost ah children gain relief from the pain and discomfort of teething by sucking or biting on a convenient object. If these objects are painted it is probable that the child will ingest some of the point. Some idea of the magnitude of the risk can be gained by considering the amount ol lead in a paint iiim which is 70 micrometres thick. A white lead linseed oil top coet of the type used twlore the last war could contain over GO per cent lead in tire dry film. 1 ho amount of lead present in an old paint film of this type would be ol tlse order of 150jig per square millimetre. A modern white lead wood primer applied at the same dry film thickness would give a load concentration ol about 100 jig per square millimetre whilst a modern decorative gloss paint (0.5 per cent lead in the dry film) would give a concentration ol 0.5 jig per square millimetre. A good toys paint (0.01 per cent lead in the dry fiiml would give > concentration of about 0.01 per cent jig per square millimetre. It has been tpown that the habitue/ ingestion of 1000 jig of lead by a child has resulted in severe clinical lead poisoning in 3- A months. The area of the four paint systems which would have to be ingested regularly is as follows: 76 micrometre paint film Ares containing , 1000 fjg of lead Objects of approximately similar area White leadlinseed oil topcoat. 7 The ci oss-sectional area of the lead in a pencil. Modern white lead wood primer. 10 The cross-scciionat area of the lead in a pencil. Modern decorative gloss. 2,000 The largest face of a match box. Good toys paint. 100,000 Vs page of Daily Telegraph- Since even themosldelerrninedchild would be unable to ingest 2,000 square millimetres of paint on a regular batit, modern decorative paints cannot be regarded as a significant hazard. however, there is a very real hazard to children who chew surfaces coaled with old lead paints or modern lead primers. The Lawthcr report makes a number of rocommendalions relating to the hazard of lead in paint, in para. 70. concern is expressed (hat high lead paints might be used in places accessible to children and that the warning laticl may not be totally effective. The report recommends that the hazard should be completely eliminated but does not suggest exactly how this might be done. Short ol banning the manufacture and use of ail lead-paints it is ditlicuH to see how tliis hazard can be eliminated Lead pigments are indispensable in the manufacture ol anticorrosive primers for Industry and there will always be the risk (hat they will be used on surtaces accessible to children. In para. 76, the report recommends that the Toys and the Pencils and Graphic Instruments Regulations should be enforced, especially with regard to Imported goods. This is a very valid recommendation and it has been our experience at the Paint RA that imported toys, particularly those originating from the Far East, often contain quantities of lead and other toxic elements which are far in excess of the permitted levels, Solutions In para 211 (<) the report recommends setting up a programme of wotk for tire detection of lead in paint coatings accessible to young children. Such information would be valuable in quantifying (lie hazard at specific locations but, inevitably, it will raise questions of whet is (he host way ol dealing with interior surfaces of a building which are found to be heavily contaminated with lead paint. This topic has been the subject of research in the United States and it appears that there are three mam solutions to the problem. The use of barrier materials. Paint removal. Replacement ol components. The barrier material method involves covering the painted surfaces to render them inaccessible. Walls can be covered with wall board, hardboard, plywood or vinyl fabric. Alternatively a thick layer of a cementitious, aggregate or textured paint can be used. Such methods can be useful (or covering painted walls but are generally impracticable for dealing with painted interior woodwork, Total removal of the lead paint it, in theory at least, the ideal solution but in practice this can present problems. Under no circumstances should dry sanding or abrasion be used since this will release lead paint dust into the atmosphere and result in widespread contamination of the building. In any case the dry rubbing down of interior lead paints is specifically prohibited by the Lead Paint Regulation 1927. 1 he paint can be removed with a chemical stripper but this can be a tedious method and (hick layers of paint may require repeated applications of stripper. There are hazards associated with the use of paint strippers: they arc corrosive materials which give oil toxic fumes and tire toxicity hazard is greatly increased by smoking. Stripping operations should be carried out in a well ventilated atmosphere by workers who are wearing adequate skin and oye protection. An alternative method ol removal is to use some suitable heat source such as a blowlamp, a gas torch or an electric heat gun. Special care must be taken not to heat the pt.nl to a level where it catches lire Otherwise lead lumes will be liberated into the atmosphere. This is definitely a task for skilled operatives working under qualified supervision. Obviously ony paint removed by stripping or by thermal means must be collected and disposed of safely. The complete removal end replacement of doors, windows, their frames and other interior woodwork is an accepted technique of lead paint abatement although it is used mainly in cases where the components are of such an age or condition that replacement is justified. If this method is employed, care should be taken to collect up any paint flakes which may become detached during die removal process. The industry has done much over the last decade to minimise the hazards to young children from lead sources in paint films. Work is still going on to find a "lead free" system which is economical and does not prosent any other risks. Until such time as this goal is achievod the best form of protection available is the warning label, a point which the EEC experts have acknowlerlged by following the UK industry's voluntary agreement with HM Government and proposing the adoption of it in the future labelling legislation. This article is based on a paper published in `Environmental Health' in October I960. We are grateful to the editor ol this journal lor permission to mproduce it as a Note to Industry. GID017966 Notes to Industry No. Title Date 1. Flash Point April 1975 2. Electron Microscopy Service August 1975 3. Information Services 4. Internal Stresses in Paint Films 5. Flame Retardant Paints February 1976 May 1976 June 1977 6. Painting Goods for Export January 1979 7. Pretreatments for Powder Coatings April 1979 8. Analysis of Air Pollution in the Production and Use of Paint and in Welding June 1980 9. Odour Problems from the Stoving of Industrial Paint Sept 1980 10. Equipment for the Application of Powder Coatings December 1980 Notes to Industry are published by the Paint R.A. and are available free of charge to Member and non-Member Companies. Please contact: Mrs. Caroline Veitch, Information Department, Paint Research Association, Waldegrave Road, Teddington, Middlesex TW11 8LD. Telephone: 01 - 977 4427 Telex: 928720 GLD017967 coatings has several oiwavnmo**.