Heavy Metal

I understand this is the name of a type of modern music. This article is not about music, but about stuff you don’t want in your body, and specifically that you don’t want in the paint on your roof or walls.

Unfortunately the definition of “heavy metal” is somewhat loose. Wikipedia provides “any metallic chemical element within the upper range of atomic weights” and then “A heavy metal is a member of a loosely defined subset of elements that exhibit metallic properties” but also “The term heavy metal has been called a “misinterpretation” in an IUPAC technical report due to the contradictory definitions and its lack of a ‘coherent scientific basis’”. So, a term we have been happily using for decades actually has an uncertain definition.

However, for the purpose of this exercise a further extract will clarify, “Living organisms require varying amounts of “heavy metals”. Iron, cobalt, copper, manganese, molybdenum, and zinc are required by humans. Excessive levels can be damaging to the organism. Other heavy metals such as mercury, plutonium, arsenic and lead are toxic metals and their accumulation over time in the bodies of animals can cause serious illness”

So we have two types – necessary to life in some form in probably small quantities, and toxic at any level and capable of being accumulated in the body. This is particularly pernicious as while a large dose has immediately obvious effects, continuous small doses have less obvious, but no less serious effects over a longer time frame. Nothing happens until the person is seriously ill.

Here we are going to discuss lead in paint, and specifically paint used to coil coat our metal roof and wall claddings; however chromium is another metal of concern for human health, and which also has relevance for paint, chromate primers having been popular for many years (because, like lead, they have good durability properties, but only for the building, not the inhabitants). This however is another story.

Lead and humans have been in close proximity for much of recorded history, and lead has been poisoning people for much of that time too.

Ancient records of lead miners indicate madness attributed to contact with too much lead. So it was known to be dangerous even 3000+ years ago, but they just ignored this and went right on using it. The Romans used lead acetate (lead sugar) to sweeten their wine (and also used lead water pipes). The makeup known as kohl contained lead oxide as did cosmetics used to whiten the face in Elizabethan times. Some Oriental traditional medicine contained lead metal. Lead in cookware (paint or metal) can contaminate food. Lead in bullets may cause damage (other than that of being shot) if it remains in the body. And finally in much of the 20th Century we have used tetra-ethyl lead in petrol as an anti-knock agent. In the late 20th and now the 21st centuries we have been taking lead out of things, except car batteries, and even here you can expect replacement with lithium (possibly more dangerous even!)

Extract from the OSH guidelines on lead in paint documentation ( system/files/resource-files/HE6018.pdf) follows -

It should be noted that the concentration of lead in domestic paints has declined dramatically in the past decades. It may thus be assumed that pre-1970 interior or exterior domestic paintwork is almost certainly lead-based, while pre-1980 paintwork may be leadbased. Post-1980 paintwork may generally be assured to have a very low lead content unless old stock or industrial specification paint was used inappropriately.

Paint formulations contain a variety of materials, several of which (such as lead, chromate and solvents) may be harmful to health under certain conditions. However, research has indicated that lead is presently the predominant public and occupational hazard associated with paint removal work in New Zealand.

Prior to 1945, white lead was extensively used as a pigment in paint, but after this date it was progressively replaced by titanium dioxide. Recognition of the hazards to health associated with lead in paint has since led to strict controls on paint lead content, and other forms of lead have since been withdrawn from paint formulations.

The following are estimates of when various forms of lead were controlled:

  • White lead (basic lead carbonate) and lead sulphate were used as white pigments in domestic paints until the mid-1960s.
  • Lead chromate (yellow pigment) was an ingredient in domestic paint until the late 1970s.
  • Red lead paint (steel primer) is known to have been used as a wood primer until the 1980s.
  • Calcium plumbate has been widely used as a roof coating for iron roofs from 1958 until the present time. It is now no longer manufactured and few stocks presently remain.

Lead water pipes tend to get coated inside with calcium carbonate and other deposits and for cold water may not have been too dangerous. Lead acid batteries have the lead pretty well contained and the acid is more of a hazard (in use, and after life they can be recycled). However, all the other uses listed above and more besides have created health hazards for centuries for humans exposed to them. And of course this is not just to humans or vertebrate life. Look at any old building with exposed lead (or indeed zinc or copper) flashings under windows – the area washed by this is clear of algae or lichen even if the rest of the roof is covered.

Only in the last 30-40 years has this been realised and lead use phased out. Indeed for lead in petrol this is even more recent- only since about 2000 has lead in petrol been totally phased-out in developed countries. Perhaps typical of lead use, lead in petrol had many very useful functions, and these have had to be replaced by other, not always as efficient, methods of achieving the same function. It is probably fair to say that the damage lead does to catalytic exhaust converters was also a reason for removal of lead. I noticed on a recent holiday in Europe that lead-containing petrol is still available in some places (no names!)

The same could be said for paint, and it can be said that paint primers containing lead did perform better than their replacements; pity about the toxicity.

So, what about the paint used for metal roof and wall claddings. Apart from the hazards common to other lead applications – toxicity among workers making the lead compounds, making the paint, applying the paint, and disposing of the paint during recycle of the coated steel, we have the issue that many people globally used painted metal roofs to catch rainwater for drinking (and for watering plants).

Both these activities have been shown to have adverse health effects of people (or plants) consuming them. Unlike ingestion in larger quantities the uptake of lead from drinking water is slow but still dangerous, and this means the symptoms may not be so obvious.

The use of paint containing lead for painted metal used for roofs has been banned and controlled since 1996 (and before). Since any pre-painted metal cladding product may be used for a roof from which drinking water is taken, this ban applies to all such product.

Back to HASNO - the following (rather detailed) extract from the regulations spells this out –

3.6 Hazardous Substances and New Organisms Act 1996 The Hazardous Substances and New Organisms Act (HSNO) and its associated regulations places controls on the import, manufacture or use (including disposal) of chemicals that have hazardous properties. This includes house paint or industrial paint containing lead. The Act requires lead-containing paint (manufactured or imported after 2006 note this late date) to be labelled with warning and hazard information. The labelling required will depend on the chemical form in which the lead is present in the paint and the amount present.

Hazardous Substances and New Organisms Act 1996 - Group Standards for Surface and Coatings and Colorants.

Under the Group Standards for Surface and Coatings and Colorants, any substance permitted that is intended for use as a paint must comply with the restrictions as set out in the Australian Uniform Paint Standard, as per Appendix 1 of the Standard for the Uniform Scheduling of Drugs and Poisons (SUSDP) No. 20. The SUSDP prohibits the manufacture, sale, supply or use of any paint with a lead content greater than 0.1 percent and 0.2 percent (percentage based on the non-volatile content of the paint) for lead and lead compounds and lead and lead compounds occurring as an impurity in zinc-based paint, respectively. The restrictions on application apply to: (1) a roof or for any surface to be used for the collection or storage of potable water; or (2) furniture; (3) any fence, wall, post, gate, building (interior or exterior), bridge, pylon, pipeline, storage tank or any similar structure; or (4) any premises, equipment or utensils used for the manufacture, processing, preparation, packing or serving of products intended for human or animal consumption.

This document makes it clear that lead above a certain level has not been allowed in roof paint since 1996, because of run-off. The other effect mentioned in several sources is that once binder of the lead containing paint deteriorates from UV and oxidative degradation the lead filler can blow or wash away as lead containing dust. (Very similar to asbestos both in means of exposure and rectification, although not health effect).

Any roof paint containing more than 0.1% lead or lead compounds and 0.2% lead or lead compounds in zinc based paints is not allowed under the HSNO legislation – regardless of whether it runs off or not. In the case of low quality paint, fading caused by UV degradation means the binder has failed and can release lead compounds into roof water.

At the 2013 AGM, NZMRM members approved the development of a new MRM coil specification, based on AS/NZS 2728 with some modifications. This will be published widely in early 2014. In the meantime, NZMRM requires that coilcoated metal cladding used by our members complies with AS/NZS 2728 Thus so it is also relevant to look at Appendix M of AS/NZS 2728:2013 (and earlier versions) – which follows the HSNO regulations above, but is specifically for coil  coilcoated cladding. This is included in the MRM coil specification.


This Appendix provides guidance on the safe applications of paint coatings on metallic substrates. The proportion of a substance for the purposes of these schedules is calculated as a percentage of the element present in the non-volatile content of the paint.

NOTE: Third schedule paint should not exceed the following limits:

(a) Lead or lead compound..................................... 0.1 per cent.
(b) Lead or lead compounds occurring as an impurity in zinc based paint............................... 0.2 per cent.

Worth noting also


A person should not manufacture, sell, supply, or use a First Schedule Paint for application to:

(a) A roof or for any surface to be used for the collection or storage of rainwater.

NOTE: First schedule paint should not exceed the following limits:

(a) Antimony or antimony compounds, excluding antimony tartrate pigments....................... 5 per cent.
(b) Barium salts excluding barium sulphate or barium metaborate............................... 5 per cent.
(c) Cadmium or cadmium compounds .................. 0.1 per cent.
(d) Chromium as chromates of ammonia, barium, potassium, sodium, strontium or zinc........ 5 per cent.
(e) Selenium or selenium compounds .................. 0.1 per cent.


A person should not manufacture, sell, supply, or use a Third Schedule Paint for application to:

(a) A roof or for any surface to be used for the collection of storage of rainwater.

The latter (M3) covers some of the other heavy metals which have been useful in and used in paints in earlier times, but are no longer allowed because of health risks discovered during the last decades of the 20th century. Strontium chromate has previously been used as a very corrosion inhibiting primer for coilcoated paints.

Use of any of these materials in paint used on coilcoated steel or aluminium roof cladding means that the products then does not comply with AS/NZS 2728, or the proposed NZMRM coil specification, or the NZ HSNO regulations.

Some overseas countries do still allow lead to be used in paint (drinking water is not collected because of other pollution), and at the same time UV resistance required is less in a less severe environment.

Therefore without the right quality controls we could see imported product which will not comply with the criteria outlined and could therefore leads to detrimental health effects for those using roof water for drinking (or even garden watering). Quality of the paint is the key component to ensure this does not occur.