Paint Toxicity and Risk
Hesaan Sheridan
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| Paint layers uncovered in a Victorian theatre to reveal fine marbling (Photo: Hesaan Sheridan) |
A small but vocal contingent in the UK is trying to persuade architects and contractors to treat lead in paint as asbestos, encouraged perhaps by a flourishing US lead abatement and mitigation industry. This lobby is assisted by a lack of independent expertise and by insufficiently robust support from the government on the subject.
Although it is true that lead paint is a hazard in old buildings that all designers and contractors should be aware of, demonising lead while ignoring the other heavy metals found in paint is simply not a good risk assessment model. Conservationists must also be mindful of the possible conflict between health risks and the preservation of significant historic features.
This article aims to set the record straight by outlining the scientific evidence for concern, and advocates the use of evidence-based risk assessments.
BACKGROUND
Lead compounds added to paint or varnish result in formidable long-lasting products. Their high opacity and tendency for even dispersal equate to good coverage and high hiding power. The subsequent dry paint film tends to be tough and durable; scratch-resilient; easily cleaned; and resistant to water, heat, UV radiation, mildew and corrosion.
Older lead paint was often sufficiently sound that it could simply be surface-prepared and overpainted, as evidenced by the myriad layers often observed when paint archaeologists investigate colour schemes in historic buildings.
Lead compounds found in paints and varnishes include:
- white pigments and fillers: basic forms of lead carbonate, sulphate, silicates and ‘leaded zinc oxide’ (zinc oxide and basic lead sulphate)
- lead tetroxide (‘red lead’) and other coloured anti-corrosive metal primer pigments including calcium plumbate, lead chromate and lead silicochromate
- lead monoxide (‘litharge’) and/or fine metallic lead
- lead chrome greens and yellows (lead chromate with/without Prussian blue pigment)
- drying agents such as lead naphthenates, acetates, and octenates (which speed up film-formation by catalysing the polymerisation of the binder).
When a ban on lead carbonate and lead sulphate in paint was proposed by the EEC in the late 20th century, the Society for the Protection of Ancient Buildings successfully lobbied for an exemption allowing its use under licence ‘for the restoration or maintenance of historic buildings and fine or decorative works of art when restoring or maintaining historic textures or finishes’.
So why was this useful and cost-effective ingredient removed from most paints? Put simply, lead bioaccumulates in and is poisonous to the human body, other animals and the environment. It is a neurotoxin capable of causing ‘lifelong, irreversible, and untreatable’ damage to our brains and nervous systems [1]. The rapidly developing neural systems and brains of foetuses, babies and children are especially susceptible. Lead can also harm the renal system leading to hypertension (high blood pressure caused by kidney disease) and can affect the haematological system by damaging red blood cells, resulting in anaemia. These and many other detrimental effects are well documented [2, 3, 4, 11, 21, 22].
UNDERSTANDING THE RISKS
High-lead paint or varnish that is in good condition or buried under newer non-lead coatings is unlikely to be hazardous provided it remains encapsulated and undisturbed. If there is no pathway into the body, there cannot be a risk of exposure. However, any redecoration, refurbishment or alteration work represents a potential risk of exposure or environmental contamination. An awareness and thorough understanding of the risks by all those involved is the key to their management.
The quantity of lead present in a building is related to its age and the accumulation of multiple coats of paint. Older buildings may also show higher levels of other toxic and heavy metals and metalloids which are no longer used as paint additives such as copper arsenate (a green colour popular in Victorian times).
The Public Health England National Poisons Information Service reports that ‘despite the toxicity of lead being well known, lead exposure remains a cause of morbidity not only in industry but also to members of the public, particularly to children’, with paint-stripping identified as the most common source for both occupational and non-occupational exposure [5].
Within the scope of The Housing Act 2004, the UK Housing Health and Safety Rating System Operating Guidance classifies lead poisoning as a ‘Class 2 harm’ (out of 7, where 1 is highest) and notes that there are indications that ‘low’ levels of lead can impact IQ in children. Immediate symptoms of workers who stripped paint in old buildings have been documented as fatigue, malaise, loss of appetite, nausea/vomiting, abdominal pain, constipation, headaches, dizziness, mental impairment, joint and muscle pain, weakness of hands and pricking or tingling sensations [25].
Para-occupational lead exposure has been documented where contractors take lead dust home, exposing their own children. The ‘harm’ resulting from lower-level lead exposure may not cause visible symptoms. Growing research over the past 20 years has indicated subclinical effects in cognition and higher systolic blood pressure in adults and IQ reduction and behavioural problems in children under four years of age, at blood levels of just 5 µg/dL (0.24 µmol/l) and even lower [6, 21, 22].
As the human body is particularly bad at removing it, lead bioaccumulates within bone and dentine [25] throughout our lifetime [31], and the US Center for Disease Control (CDC) considers that there is no known safe level of lead in the body. In general, our blood lead level (half-life 35 days) represents only two per cent of our total lead loadings, while bone and dentine lead levels (half-life 20-30 years) represent 95 per cent [25]. There is also evidence that lead within bone is re-released into the blood during pregnancy [32], at times of stress or poor nutrition, or as we age [31].
However, lead is not the only toxicant to be found in paint or varnish. Within the multiple layers of older paints, a cocktail of toxic and heavy metals and metalloids is possible, resulting in significant potential for multiple metal contamination [27]. Although cadmium was banned in the UK in 1993, many other toxic ingredients are reliant on post-2007 EU REACH for regulation. Lead chromate, zinc chromate, cadmium sulphide yellow, chromium trioxide, copper arsenate, arsenic disulphide, antimony trioxide, cadmium sulfoselenide red, and impure barytes are all possible ingredients within architectural paint films. The toxicities and environmental impact of these and other ingredients should not be underestimated; the first four are on the REACH list of substances of very high concern (SVHC). Simultaneous exposure to multiple heavy metals may produce a toxic effect that is additive, antagonistic or synergistic [7, 23].
Mercury was added to paint for its biocidal and preservative properties, and where found in conjunction with lead could have grave toxicological implications due to its suspected synergistic toxicity with lead [8]. Mercury was replaced as a preservative in emulsion paint in the UK by substances such as ammonia and organic based preservatives, over a period of years from the mid-fifties to the late seventies [26].
Asbestos may be found in textured coatings and fire resistant paints such as those used to line the escape routes of theatres, cinemas and other public buildings, and a report by the International Agency for Research on Cancer (IARC) on the occupational exposures to carcinogens in paint manufacture and painting highlights its use as a paint filler more generally [28].
HISTORY OF CONTROL
In order to appreciate the risk from lead in architectural paint, it is important to clarify the history. Contemporaneous developments in the US are often confused for UK and European initiatives, and misunderstandings also arise from the fact that the definitions of what constitutes ‘high-lead paint’, ‘low-lead paint’ and ‘lead-free paint’ have changed over time. For example, BS4310:1968 defined low-lead paint as being up to 1.5 per cent lead in the dry paint film, while in 1983 the Royal Commission on Environmental Pollution [11] commented that ‘even one per cent of lead is a high level’. Modern research would suggest that far lower levels can be significant if the paint is disturbed and adequate control measures are not applied.
While the 1930s and 40s saw the highest lead concentration in paints, levels in most paints fell dramatically in the following decades. In 1963 and again in 1974, voluntary agreements between the Paintmakers Association of Great Britain (now the British Coatings Federation) and the government resulted in the labelling of paint which contained more than 1.5 per cent (15 g/kg) in 1963 and one per cent (10 g/kg) in 1974 of lead in the dry film. The agreements were embodied within BS4310 but paint which did not comply with the British Standard could still be sold.
The European Directive 77/728/EEC introduced in 1984 focused on consistent and reliable labelling rather than on banning high-lead paint. Labels were required to carry a warning that the paint contained lead or any other known toxicant and should not be used on surfaces liable to be sucked or chewed by children. It has been acknowledged that the 1984 regulations may not have directly affected the supply of leaded paint nor controlled its use and that the growing DIY market was a potential concern [11].
Wood and metal primers, imported paints and exterior paints [11] were not subject to formal regulation, while household decorative gloss paints, undercoats and varnishes continued to have lead-based driers added in concentrations below one per cent in the dry paint film [33]. However, the availability of cheap viable alternatives such as titanium dioxide certainly helped to reduce or exclude lead-based compounds in indoor decorative paint finish coats.
The Environmental Protection (Controls on Injurious Substances) Regulations 1992 implemented Directive 89/677/EEC. The legislation was specific to lead carbonate and lead sulphate rather than the full spectrum of lead pigments and driers. Similar UK legislation for cadmium in paint followed a year later. These were superseded by the Controls on Dangerous Substances and Preparations Regulations 2006 and ensuing amendments.
EU REACH took effect in 2007. Annex XVII of the regulation took effect in 2009. The UK and EU countries adopted REACH, which takes a more complex chemical-specific approach rather than implementing maximum lead limits in architectural paint. However, the use of lead compounds by ‘professionals’ is permitted, subject to labelling restrictions. Other countries adopted the pragmatic view that it is the lead ion itself that causes the harmful effect and limited the total lead content of paint to between 0.009 per cent (90 mg/kg) and 0.06 per cent (600 mg/kg), allowing for impurities in the ingredients [9, 19].
Lead chromate, lead sulfochromate yellow and lead chromate molybdate sulfate are subject to an authorisation procedure which currently still allows special use (for example, for road markings) [9].
UK Legislation
Despite the hazard, legislation in the UK to control lead and toxic metal exposure and contamination from paint is far from straightforward, and the lack of official UK specific information and robust HSE and PHE guidance has been criticised in some quarters [20]. We have wide-ranging health and safety legislation such as The Construction (Design and Management) Regulations 2015 (CDM), which puts a duty on the principal designer or contractor to identify and eliminate, as far as possible, foreseeable health and safety risks to any person. This specifically mentions ‘lead paints and special coatings’ as potentially hazardous materials. Others include the Management of Health and Safety at Work Regulations (MHSWR) and associated HSG65.
Occupational exposure to lead is embodied within The Control of Lead at Work Regulations 2002 (CLAW) and its associated Approved Code of Practice (ACOP) while other toxic metals are covered by Control of Substances Hazardous to Health Regulations. COSHH defers to CLAW in relation to lead but is relevant to other toxic metals in paint. Potential significant exposure of other affected persons (the public, visitors and the end-user) must also be considered.
Frequently, the requirements of UK legislation are confused with those of the US and while the US has a well-developed lead-abatement industry, this is not helpful to those seeking to ensure clarity and compliance with UK legislation. There are certain vagaries of US legislation that may not be appropriate for wholescale import to the UK. Lead paint test results are often expressed in the US on a mass-area (mg/cm2) basis and this is frequently cited by those who wish to promote the proliferation of powerful radioactive X-Ray Fluorescence (XRF-i) instruments in the UK. However, the accepted means of paint analysis and regulation for lead and toxic metals in the UK and within international regulatory limits for paint is mass-mass/weight-for-weight basis (%, mg/kg or ppm) [9]. This is further confirmed by the CLAW ACOP which makes clear preference for methodologies based on BS3900 mass-mass test methods.
The WHO acknowledges the superiority of laboratory testing over ‘in the field’ portable XRF testing [10], which became popular in the US. The UK CLAW legislation prioritises blood or urine lead surveillance and lead-in-air monitoring, while US HUD legislation [12] is centred on wipe sampling and settled dust testing as a means of clearance for lead paint projects. Saliva medical surveillance, sometimes used in the US, has no credibility under CLAW and has been shown to be unreliable [17, 18].
It is unsurprising that the construction and refurbishment industry is not confident in its approach to awareness and control of lead and toxic metal exposure from paint and varnish. The full requirements of CLAW are triggered if there is a potential for ‘significant exposure’ of any persons affected by the work. This includes medical surveillance and air testing. Paint disturbance and removal is frequently referred to in CLAW and its code of practice as work subject to its control because it is likely to cause significant exposure. While it also indicates that materials containing less than one per cent lead may not be significant, the main point is that the exclusion depends on the process employed and the control measures applied.
A lead and toxic metals in paint survey which identifies the general levels and distribution of paint toxicants can inform risk assessment, containment and waste management measures. However, the key requirement of UK legislation is the risk assessment, not the survey. This is confirmed by current HSE website FAQs which specifically state that a lead paint survey is not a legal requirement [13].
MANAGING THE RISKS
Refurbishment or redecoration may represent a substantial risk factor for exposure to and contamination by lead and other toxins. However, with careful planning, preparation and implementation of site-specific measures and controls, the potential hazards are not prohibitive and the risks can be managed effectively.
A plan for the management of the risks is suggested in the flow chart below. The lowest risk options are associated with minimally invasive procedures, but if stripping is required the safest available option should be selected and the control measures tailored to that option. All exposure pathways should be considered but the most hazardous processes are those that generate airborne dust or fumes. The resulting contaminants are difficult to contain and are easily absorbed, giving rise to both inhalation and ingestion risks. They also generate the highest potential for the contamination of clothing, surfaces and the environment. However, a ‘wet process’ that eliminates airborne particulates may still carry some risk of contamination and ‘significant exposure’ from ingestion, while chemical stripping methods that dissolve the coatings may present an additional skin absorption risk.
There is evidence that unacceptable levels of lead dust can arise from removal of paint with lead contents of 0.25 per cent or lower [14]. In 2008 the Health Protection Agency (now Public Health England) reported that cases of lead exposure in children associated with paint have occurred at levels of 0.1 per cent [15].
The important thing to note is that lead in paint or varnish does not suddenly become non-hazardous at one per cent (10,000 mg/kg) or even at 0.1 per cent (1,000 mg/kg). The scale of risk also depends on the levels and types of other toxic and heavy metals present, the quantity and thickness of paint present, the method used to disturb or remove it, and the measures taken to protect all those affected by the work or the contamination arising from that work. This includes avoidance of contamination of the indoor and outdoor environment, soil and surface water systems.
If the risk factors are known, standard risk assessment models (following COSHH principles for example) can be applied to reliably assess the risk and identify the site-specific measures required to minimise it. Where severity is high, exposure levels should be kept low. How low depends on the likelihood of harm and knowledge of the harmful effects of exposure. Control measures should address both acute and chronic health risks.
In conclusion, paint or varnish should never be regarded as a completely inert or harmless substance. The risks need to be better evaluated and understood before work starts in order to effectively manage them. However, attempts to spread alarm or promote a lead remediation industry are not helpful and should be treated with caution because proper risk assessment requires a more holistic approach [24].
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Further Information
International POPs (Persistent Organic Pollutant) Elimination Network: Lead |
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G Cullen et al, Monograph for UKPID: Lead, National Poisons Information Service, 1996 |
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L Knott, 'Lead Poisoning', Patient, 2015 |
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Health Canada, Final Human Health State of the Science Report on Lead, 2013 |
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D Brackenridge et al, ‘Non-occupational and occupational lead exposures reported to the UK National Poisons Information Service 2008-2010’, Clinical Toxicology, Vol 50, 2012 |
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I Kar-Purkayastha et al, 'Lead: ongoing public and occupational health issues in vulnerable populations: a case study', Journal of Public Health, Vol 34:2, 2012 |
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PB Tchounwou et al, 'Heavy metal toxicity and the environment', in A Luch (ed), Molecular, Clinical and Environmental Toxicology / Experientia Supplementum, Vol 101, 2012 |
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J Shubert et al, 'Combined effects in toxicology – a rapid systematic testing procedure: cadmium, mercury and lead', Journal of Toxicology & Environmental Health, Vol 4:5-6, 1978 |
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UN Environment Programme, Global Report on the Status of Legal Limits on Lead in Paint, 2016 |
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World Health Organisation, Brief Guide to Analytical Methods for Measuring Lead in Paint, QV 292, 2011 |
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Royal Commission on Environmental Pollution, Lead in the Environment, HMSO, London, 1983 |
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US Department of Housing and Urban Development, The Lead-Safe Housing Rule, 2017 |
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Health and Safety Executive, Frequently Asked Questions on Lead (accessed October 2017) |
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Australian Standard AS 4361.2-1998, Guide to Lead Paint Management Part 2: Residential and Commercial Buildings, 1998 |
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Health Protection Agency, 'Lead poisoning cases associated with environmental sources', Chemical Hazards and Poisons Report, Issue 11, 2008 |
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Environment Agency, Waste Acceptance at Landfills, 2010 |
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EK Silbergeld, 'New approaches to monitoring environmental neurotoxins', Annals of the New York Academy of Sciences, Vol 694, 1993 |
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D Koh et al, ‘Can salivary lead be used for biological monitoring of lead exposed individuals?’, Occupational and Environmental Medicine, Vol 60, 2003 |
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United Nations Environment, Model Law and Guidance for Regulating Lead Paint, 2017 |
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R O’Neill, 'Dangerous Lead: Special Report', Hazards Magazine, Nov 2009 |
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WHO Regional Centre for Environmental Health Action, Lead FAQs (accessed October 2017) |
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K Chandramouli et al, 'Effects of early childhood lead exposure on academic performance and behaviour of school age children', BMJ, Vol 94:11, 2009 |
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JG Hengstler et al, 'Occupational exposure to heavy metals: DNA damage induction and DNA repair inhibition prove co-exposures to cadmium, cobalt and lead as more dangerous than hitherto expected', Carcinogenesis, Vol 24:1, 2003 |
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JL Dorne et al, 'Human risk assessment of heavy metals: principles and applications', Metal Ions in Life Sciences, Vol 8, 2011 |
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JN Gordon et al, 'Lead poisoning: case studies', British Journal of Clinical Pharmacology, Vol 53:5, 2002 |
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ST Kolev et al, Monograph for UKPID: Mercury, National Poisons Information Service, 1996 |
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HW Mielke et al, 'Multiple metal contamination from house paints: consequences of power sanding and paint scraping in New Orleans', Environmental Health Perspectives, Vol 109:9, 2001 |
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International Agency for Research on Cancer, 'Occupational Exposures in Paint Manufacture and Painting', IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 47, 1989 |
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Centers for Disease Control and Prevention, Lead, 2017 (accessed October 2017) |
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BA Chowdhury et al, 'Biological and health implications of toxic heavy metal and essential trace element interactions', Progress in Food & Nutrition Science, Vol 11:1, 1987 |
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CP Holstege, 'Pathophysiology and Etiology of Lead Toxicity', Medscape, 2015 (accessed October 2017) |
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H Hu et al, 'Lead, bones, women, and pregnancy – the poison within?', American Journal of Epidemiology, Vol 156:12, 2002 |
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Department of the Environment, Pollution Paper No 19: Lead in the Environment – The Government Response to the Ninth Report of the Royal Commission on Environmental Pollution, HMSO, London, 1983 |
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