BACKGROUNDIn view of recent comments in the press which are tending to put the position of lead and paint into an unfortunate limelight I feel that a summary of the current situation is necessary to get the correct perspective. Recent press releases give the impression that all paint contains lead and so paint per se is toxic. One sees now why the Press cannot be taken seriously as again they have gone off half-cock and it is necessary to put the record straight.First it must be understood that lead is an accumulative (chronic) toxicity and accumulates in the body. Lead is a common element and is widely spread in nature and under normal circumstances the body excretes it and so levels do not increase and the body can cope with naturally occurring amounts. In order to have an effect however lead has to be in a form that can be digested and to get into the system Lead as a metal is relatively inert and was used since Roman days as such things as water pipes. If there is acidity in the water however some lead will be dissolved and so cause problems. The Romans did use lead vessels for wine storage until they discovered that the acid in the wine could react with it – formation of Lead Acetate. The problems of lead poisoning have been around for a long time!
It is this solubility of certain lead compounds in the stomach acid that is the problem. If the lead is in such a form that it is not soluble in acids then there is no problem. It is quite safe to continue using that beautiful lead crystal glassware! Lead has also been used in glazes for pottery and gives effects difficult to produce otherwise and it has been established when properly used it presents no problem to the user. If the solubility of a lead compound in acid is such that the stomach acids can dissolve or convert it then it is considered as toxic.
As defined in the Dept of Labour Lead Regs. “lead paint” means any paint, primer, paste, spray, stopping, filling or other material used in painting, which, when treated in accordance with the health and safety standards, yields to an aqueous solution of hydrochloric acid a quantity of soluble lead compound exceeding five percent of the dry weight of the portion taken for analysis when calculated as lead monoxide;
In this way it is not the total amount of lead that is so important but the amount of soluble lead!
Children have a much faster metabolism than adults and a smaller body mass and so are more prone to the effects. Add to this the built in desire to shove everything in their mouths and we can see a greater problem.
THE PROBLEMThe problems of lead in paint and the effect on children arose some time ago when white lead was widely used in wood primers. Children would chew on windowsills in particular and this was exacerbated by the fact that the compound of lead in the paint had a sweet taste.
Lead has been used in paints in three ways : –
- As an aid to speed up drying. (The quantities involved are minimum nevertheless this has been eliminated in paints for decorative purposes by SAPMA members and they have placed warnings on the cans of any paints at below this level )
- As an anticorrosive agent. Lead in some forms, (White & Red Lead) have been used for years, as they are excellent for protecting wood and steel. Their use has now been discontinued. When used as anticorrosive pigment took the form of an oxide, sulphate or carbonate, all of which are very soluble in acids in the stomach. Currently the greatest problem with these coatings lies in its removal when repainting is necessary.
- As a coloured pigment. Lead based pigments in the form of chromates and similar compounds still remain the most cost-effective method of obtaining stable, bright and durable coatings. One reason for their good performance as pigments lies in their chemical stability. They are much less toxic than Red and White Lead as their soluble lead content is lower and they are used in lesser amounts. See definition above of soluble lead.
Leads compounds encountered in the paint industry, past and present, are
- Oxides Carbonates Hydroxide
- litharge and red lead
- White lead (Carbonate/hydroxide) White lead (Carbonate/hydroxide)
- High soluble High soluble High soluble
- Sulphate Chromates Plumbates Driers
When evaluating lead levels in paint this must be done on a basis of soluble lead and total lead. A further complication comes from the fact that paints are supplied in admixture with volatile solvents and other hazardous substances so consideration has to be given to this aspect. This means that the toxic lead content has to be calculated as soluble lead on the non-volatile content. When it is considered that the dried paint film means that the lead is encapsulated in the dried binder, generally a very stable plastic substance, the quantity of lead that can be leached out in the stomach is very small. Most ingested dried paint must go straight through the body.
A total ban on lead paints as shown in the proposed legislation would be counter-productive. It must be obvious to all that road line paints need to be based upon highly visible colours and to have excellent durability. The same can be said for heavy earth moving machines, fire engines, communication masts and the like. The Dept of Health have therefore targeted coating used by the domestic market for strictly decorative reasons which are less susceptible to environmental exposure problems.
WHAT ARE THE DANGERS?We must consider the vast quantities of lead which have been put into the atmosphere in the last eighty years by petrol engines When petrol passes through it is effect burnt and the lead compounds contained in it are expelled into the air in the form of lead or its oxide in the form of fine particulates. Over a period it could be expected that this would react with the carbon dioxide in the air to form the carbonate and so remain equally toxic. A search of the web will show how this lead contamination is widespread and has got into the food chain. Just as in the case of global warming our past is catching up with us. This dust is all over then and problem must be more one of lead on paint rather than lead in paint. Good old-fashioned sanitation can be an answer here. Use a vacuum cleaner or a damp cloth – not a duster to clean. Perhaps the question of hygiene is the reason for the report that there is a higher incidence of lead levels in townships – they do not have the facilities there.
ou live in a building which is more than 30 to 40 years old then the woodwork might have a lead primer or if the finished colour and is bright yellow, orange, red or green then there could be lead present. So if it is do not eat it – let sleeping dogs lie. The general rule is as always “never remove paint in good condition” – clean it and rub it down with fine sandpaper then paint over it. If it is flaking and in bad condition or is so heavy as to stop windows or doors from closing then it will need to be removed. If you have reason to suspect that lead may be present extra care must be taken.
Abrading the paint will produce dust and, lead or no lead it, would be unwise to breathe this dust and so a dust mask should be used. It is also advisable to avoid skin contact and cover the hair.
The alternatives to this are the use of paint removers or heat guns. Both of these present problems and care must be taken to use paint removers from reliable manufacturers with proper guidelines on the labels. In the case of the use of heat guns again precautions are needed. Heat should soften and blister the paint making it easy to scrape off and fumes can be produced if over heated. Only sufficient heat should be used to loosen the paint – try to avoid burning the paint. It is wise to use a respirator and cover up and have a fire extinguisher handy. Once cool and safe put scrapings into a plastic bag for disposal.
Modern paint technology continues to follow the green road and continues to produce more environmentally coatings without sacrificing quality and durability. It must be obvious from the fact that more and more water based coatings are coming onto the market as research and development continues. The Paint Manufacturers Members do all they can to produce fool-proof coatings but cannot produce blood-fool proof products. Make sure that the materials you purchase are from reputable sources and read the label before you purchase.
Let us hope that the Governments current initiatives in legislation to control lead in paint used on children’s toys will have the desired effect and there can be no doubt that it is step in the right direction. The lower lead usage in fuels will affect the issue even if it is too late to curb the damage done. But in the same way as stricter licensing of firearms does not affect thieves, robbers and murderers, any reduction in the availability of firearms will contribute to the end result. The public must place its confidence in organisations such as the White lead (artists colours – historical) red, orange, yellow and green pigments.
Lead salts of various organic acids
High Soluble Low Soluble Mod Soluble High Soluble
are chromates, molybdenates & sulphosuccinates, along with plumbates and
Paint Manufacturers Association and should not be mislead by mass media suggestions from unqualified sources.
LAF Sept 2009