Guidance

Lead: environmental and public health intervention

Published 8 October 2024

Roles and responsibilities

Health care professionals at UK Health Security Agency (UKHSA) and local authority public health teams will be notified if a child under 16 years of age has been tested for lead in their blood and the concentration is at or above 0.24 µmol/L (5µg/dL) and they are residents in England. At this ‘intervention concentration’ the lead exposure is unlikely to be background and indicates potential source or sources of lead that are affecting them.

For adults, public health will be notified at or above 0.48µmol/L (10µg/dL) unless the case is a pregnant woman. For pregnant women there is a risk to the unborn child, therefore the intervention concentration is set at 0.24 µmol/L (5µg/dL) as for children.

Notification assists public health to liaise with clinicians such as GPs or paediatricians to find and mitigate the source of lead, by working with local authorities to investigate and offer remediation advice to homeowners or landlords.

If the source is potentially from drinking water, the local water company can test residential supplies for lead free of charge. They can be called, and a mutually agreed time arranged for testing. If the water company finds failures in the supply they will inform UKHSA or the local authority Environmental Health Officer (EHO).

For occupational lead exposure, please see the Health & Safety Executive’s (HSE) website. Exposure to lead in the workplace may come under the Control of Lead at Work Regulations, and where a workplace is responsible for testing blood lead concentrations if employees have been exposed.

Trading Standards are responsible for the identification and notification of consumer products, such as such as traditional remedies (for example, surma, kohl, imported spices), which may contain lead.

Blood lead intervention concentration

UKHSA lowered the public health intervention concentration for lead from 0.48μmol/L (10μg/dL) to 0.24μmol/L (5μg/dL) for children under 16 years and for pregnant women, with effect from 5 July 2021. The background to the change is described in the report Evaluation of whether to lower the public health intervention concentration for lead exposure in children.

The public health intervention level for lead has been lowered over time to reflect both the gradual decline in population exposure and the new evidence that lead exposure in children is associated with toxicity at very low blood concentrations. Lead exposure is associated with neuro-behavioural impairments at blood concentrations of 0.24μmol/L (5μg/dl) and even lower (1, 2).

This recommendation is based on estimates in pre-school children who have the highest lead concentrations, to maximise the detection of children most likely to benefit from public health action. Lowering the intervention concentration for lead will identify children in the top 2% of the population range and would have a net positive impact on health inequalities.

The public health invention concentration across England, Wales and Scotland for children is now the same at 0.24 µmol/L (5µg/dL).

Blood level concentration advice

While there is no defined threshold for the harmful effects of lead in children, a blood lead concentration (BLC) of over 0.1μmol/L (2μg/dL) to 0.24μmol/L (5μg/dL) is now widely accepted in the UK as the clinical threshold above which investigation should occur and a source should be identified. At concentrations at or greater than 5μg/dL (0.24μmol/L) UKHSA should be informed in England (other public health agencies should be informed in other nations), and clinical and environmental monitoring should be initiated with systematic identification of potential sources, identification of other vulnerable individuals and further monitoring.

The most important aspect of treatment is removal from exposure. Identification of the source of exposure may prove a challenge and requires a detailed history and often a degree of investigation and persistence, acknowledging the principal sources of exposure. Remember that the source may be at school, a relative’s or other frequently visited property.

Although the symptoms and signs are often not evident until children have BLCs of over 1.45μmol/L (30μg/dL), symptoms at this concentration are most likely to comprise anaemia, abdominal pain, constipation and headache. Weight loss or failure to thrive has also been reported. Children may also display increased irritability and reduced concentration.

Once absorbed, lead is distributed in the blood to bone, teeth and soft tissues (like the liver) independent of route of exposure. In adults and children, around 90% and 70% respectively of the total body burden of absorbed lead is stored in bone. Following chronic exposure, lead becomes deposited, in the form of insoluble lead phosphate, in areas of the skeleton that are rapidly growing, such as the radius, tibia and femur. Characteristic ‘lead lines’ may be seen on X-ray, and their width is related to duration of exposure (3).

The longevity of bone cells and the affinity of lead for bone are reflected in the long half-life, which is approximately 10 to 30 years, in bone. The half-life of lead in blood and soft tissues is approximately 20 and 40 days respectively. Lead is excreted in urine and faeces, also independent of the route of exposure.

Clinical interventions

The clinician will make a note on the child’s clinical history by asking appropriate questions. Clinicians should specifically ask if a child is showing any pica behaviour and should have a particularly low threshold for screening for lead exposure in children with learning disabilities or behavioural disorders as pica may be harder to identify in these cases. Pica is an eating disorder that involves eating items that are not typically thought of as food and that do not contain significant nutritional value, such as hair, dirt, and paint chips (4, 5).  

A clinician may recommend supplements or seeing an occupational therapist for pica reduction, and the parents or carers will be asked about risk factors and potential sources of lead exposure. Depending on the blood lead concentrations the child is likely to have a further blood test after 4 weeks to identify if mitigation is working.  UKHSA are generally involved until the BLC drops to below 0.24μmol/L (5μg/dL) .

Lead in the home

The Housing Health and Safety Rating System (HHSRS) is a tool which is used by Environmental Health Practitioners to assess the risk (likelihood and severity) of a hazard in residential housing to the health and safety of the occupants or visitors, and was introduced under the Housing Act 2004 for England and Wales. The assessment identifies 4 classes of harm and lead poisoning is considered as a class 2 outcome (severe). Housing officers or Environmental Health Departments in the local authority are the enforcement departments of this legislation and can serve an improvement or prohibition notice to private or public landlords. The scoring system for hazards is prescribed by the Housing Health and Safety Rating System (England) Regulations 2005 (SI 2005 No 3208) and is also set out in the statutory HHSRS Operating Guidance for local authorities.

The hazard profile for lead exposure in the HHSRS identifies 2 main sources as lead paint and water pipework (or lead-based solder or non-compliant fittings). It also references that lead will dissolve in water that has high plumbosolvency (ability of water to dissolve lead). It also identifies soil as another potential source of lead especially where there is flaking external paint.

While the HHSRS covers children in properties, it does not take into account children with pica. Therefore, it may not be known that lead paint is present below current paint surfaces and the lead not identified.

Sampling paint and the home for lead

If a child is identified as having blood lead levels above 0.24μmol/L (5μg/dL), then UKHSA may put in place a multi agency team to investigate the cause. If a source or sources are identified the multi-agency team may discuss testing to confirm the presence of lead.

Importance of testing

It may be necessary to test whether existing paint on surfaces in homes or other potential sources contain lead in order to conduct a public health risk assessment and put into place any mitigation measures.

Lead is now prohibited as an ingredient of paint used in domestic settings, however until the 1950s, UK paint may have contained up to 50% lead by weight (500,000mg/kg), which is potentially capable of causing lead poisoning in a small child if they ate just a single chip. Leaded paint at these concentrations may still be found in non-remediated Victorian properties. Voluntary agreements and legislation, such as the 1968 British Standard to label paint with lead concentrations less than 15,000mg/kg or 1.5% by weight as ‘low-lead paint’ and the eventual prohibition of any added lead in 1992 (except in specialist paints), have considerably reduced the likelihood of exposure to lead from paint.

Flaking paint, paint chips and powdered paint are major sources of lead exposure in older buildings. If the paint is in good condition or the property has been redecorated, then the lead should be sealed in and there should not be an exposure pathway. Exposure is only likely if the paint is deliberately exposed during renovation, or the paint is flaking, or through children picking or chewing at it.

Other domestic sources of exposure to lead include:

• food (for example, imported spices)
• drinking water
• traditional medicines
• cooking pots and utensils (especially pewter) brought into the UK from other non-EU countries

Testing considerations

When carrying out an investigation there may be a variety of samples which need to be collected and sent to a specialist laboratory for testing, including environmental samples (such as soil, water). It is important to ensure wherever possible that the laboratory is following a certified process and that a UK approved accreditation service is used, to ensure laboratories meet international standards and defined quality requirements.

Environmental sampling needs to be undertaken by specialists who understand how to sample environmental media, prevent cross contamination, and use appropriate labelling and containers so as not to affect the analytical results.

Public health scientists would not generally undertake the sampling, but once the samples are analysed, they would help interpret the results.

Sampling in the home for sources of lead

Recommended sampling methods

In the UK we follow WHO recommended sampling techniques with results reported as mg/kg (6). Handheld X-ray fluorescence (XRF) spectrometry provides qualitative analysis and can be used to help detect the location of any potential lead as it is non-destructive of surfaces, but in order to conduct a public health risk assessment laboratory quantitative analysis is required as mg/kg. A standard operating method should be followed and may include:

• collecting all layers of paint as lead is more likely to be present in the lower levels
• avoiding collecting any substrate materials underneath as much as possible as they may impact the results, unless the paint is flaking
• collecting several samples in different areas
• repairing any areas where samples have been taken to avoid further exposure

Sampling methods not recommended

There are a number of unit measures and qualitative and quantitative sampling and analysis techniques that UKHSA would not recommend.

Units

We recognise that some countries (such as the USA) use mg/kg² but these units are not interchangeable and therefore cannot be used to conduct an appropriate public health risk assessment.

There is no precise relationship between laboratory measurements of paint on surfaces expressed as ppm and as mg/cm² because of variations in the composition and thickness of the paint and the possible inclusion of substrate material during the analysis (6).

Test kits

UKHSA does not recommend chemical test kits as they are not accurate or precise like laboratory methods and rely on a colour change to indicate presence or absence of lead.

These kits have many limitations which may include:

• not meeting UK analysis accreditation results not being based on UK thresholds
• not providing lead concentrations (qualitative just presence or absence)
• needing to score or remove a chip of paint for testing (potentially exposing the lead)
• challenging to identify a colour change with some paint colours
• possibly producing false results
• subjectivity of result interpretation

We also do not recommend the use of dust wipe sampling, a method used by the US Environmental Protection Agency, which is based on the size of the area sampled and results are compared to USA thresholds which are different to the UK.

References

1. World Health Organisation (WHO). Childhood lead poisoning 2010: pages 1 to72

2. Lanphear BP and others. Low-level environmental lead exposure and children’s intellectual function: an international pooled analysis Environmental Health Perspectives 2005: volume 113, issue 7, pages 894-9. Erratum in: Environmental Health Perspectives September 2019: volume 127, issue 9, page 99,001

3. International Programme on Chemical Safety (IPCS). Lead Monograph for UK Poisons Information Database

4. National Eating Disorders Association (NEDA). About Us (Viewed on 28 October 2022)

5. National Autistic Society. Understanding and managing pica 2019 (Viewed on 28 October 2022)

6. World Health Organisation (WHO). Brief guide to analytic methods for measuring lead in paint 2020