Guidance

Lead: clinical intervention

Published 8 October 2024

Changes to public health concentration intervention

The public health intervention concentration has changed. This is for 2 reasons.

Firstly, at blood lead concentrations (BLCs) between 0.24 to 0.48 μmol/L (5 to 10 μg/dL), there is strong evidence for adverse effects on cognitive function in children, as well as the occurrence of externalising behaviours (for example aggression, hyperactivity), and delay in sexual maturation or puberty onset in adolescence. There is also evidence for adverse health effects to the foetus of in utero lead exposure at maternal BLC <0.48 μmol/L (<10 μg/dL). Therefore, a precautionary approach to minimise in utero exposures is advised.

(It is also important to note that there is no evidence of a threshold for lead-induced developmental neurotoxicity in children. For example, BLCs of as low as 2 μg/dL have been reported to cause developmental neurotoxicity.)

Secondly, although population exposure to lead has decreased significantly due to successful primary prevention efforts, there is still an estimated 6% of children that have a BLC ≥0.24 μmol/L (≥5 μg/dL). These children are more likely to be exposed to a higher, definable source of lead that can be identified and mitigated, rather than multiple very small exposures that may occur in the wider population. Evidence strongly suggests that high lead exposure in England is associated with multiple facets of inequality, including economic, health, age, and ethnicity dimensions. Therefore, reducing harm from lead exposure in these children is likely to positively impact on these inequalities.

Therefore, UKHSA will become involved in source reduction and mitigation, at:

• ≥5 μg/dL (≥0.24 μmol/L) in children under 16 years old, resident in England

• ≥5 μg/dL (≥0.24 μmol/L) in pregnant women (protection of foetus)

• ≥ 10μg/dL (≥0.48 μmol/L) in adults, resident in England

Participating laboratories will report results of children under 16 years old with a BLC of ≥0.24 μmol/L (≥5μg/dL) to the UKHSA Lead Exposure in Children Surveillance System (UKHSA LEICSS).  Pregnant women with a BLC of ≥0.24μmol/L (≥5 μg/dL) and adults with a BLC of ≥0.48 μmol/L (≥10 μg/dL) may be reported to the local health protection teams (HPTs) directly by clinicians.

There are several online resources to assist the conversion of BLCs, however:

• 1 μg/dL = 0.0483 μmol/L

• 1 μmol/L = 20.703934 μg/dL

Or manually transform BLC conventional units (μg/dL) and SI units (μmol/L):

• to convert conventional units (μg/dL) to SI units (μmol/L) – divide by 20.703934

• to convert SI units (μmol/L) to conventional units (μg/dL) – divide by 0.0483

Normal blood lead concentration

European data suggests that mean BLC for 1 to 6-year olds is around 0.07 μmol/L, with a 98th percentile of 0.24 μmol/L (5 μg/dL), and a 95th percentile of 0.17 μmol/L (3.5 μg/dL). Therefore, BLCs are unlikely to drop to zero.

While there is no defined UK threshold for the harmful effects of lead in children, a BLC of ≥0.1 μmol/L (≥2 μg/dL) to <0.24 μmol/L (<5 μg/dL) is now widely accepted as the clinical threshold above which investigation should occur and a source should be identified (see Health effects of severe lead exposure below).  At ≥0.24 μmol/L (≥5 μg/dL) UKHSA should be informed and clinical and environmental monitoring should be initiated with systematic identification of potential sources, identification of other vulnerable individuals and further monitoring.

Why is lead exposure important and why should we test for lead?

Symptomatic lead poisoning in children is most likely to present with anorexia, abdominal pain, constipation and headache. Weight loss or failure to thrive has also been reported. Children may also display increased irritability and reduced concentration. Anaemia may develop in more severe cases as a result of lead induced inhibition of haem synthesis. Lead-induced anaemia may be normochromic or microchromic and normocytic or microcytic. Lead-induced encephalopathy is now very rare but still seen occasionally in very severe cases of poisoning.

During pregnancy lead crosses the placenta and can have a similar effect on the developing foetus. Exposure to high concentrations of lead in pregnancy has also been linked in some studies to miscarriage, impaired intrauterine growth, and premature labour. It is therefore recommended that pregnant women avoid exposure to high concentrations of lead, for instance by using protective equipment if stripping old paint, or at work if they are at risk of lead exposure.

Common sources of lead exposure for children in England

Lead can be absorbed by ingestion of lead-containing particles or inhalation of lead dust or fumes. Ingestion of lead-containing paint remains the most common source of exposure identified in children with elevated BLCs, as lead was frequently used in domestic paints up until the mid-1960s (with a few minor uses continuing into the 1980s). Children may therefore be exposed by eating paint (pica) in older properties, such as peeling layers of paint from skirting boards, banisters, windowsills or radiators. Renovation or redecoration is a further means of exposure if removal of old paint involves production of lead flakes or dust (for example, through sanding) or fumes produced (such as from heat stripping) that may be ingested or inhaled.

Lead ingestion may also occur from sucking or chewing painted objects such as toys that do not comply with the EU Toy Safety Directive (Council Directive 2009/48/EC) and may therefore contain lead-based paint. Cooking with lead-glazed earthenware has also caused lead poisoning by ingestion.

Lead may also be a contaminant in traditional or natural remedies and supplements, spices and cosmetics. Soil and water are other potential sources of lead ingestion, though significant lead-contamination of domestic water supplies is rare.

Signs and symptoms of lead poisoning in children

The diagnosis of lead poisoning requires a high index of suspicion since there may be no symptoms or overt clinical signs in those with mild disease. Children with pica (which may co-occur with autism and other neurodevelopmental disorders), or who are crawling, or pre-school age, accounted for most cases notified during a UK public health surveillance study. Migrant or refugee status is also an established risk factor. Additional important risk factors for raised BLC (from a review of mainly USA data) include degraded or recently renovated older housing, residence near to lead environmental hazards, and iron, zinc and calcium deficiency. Acute severe lead poisoning is rare but should be considered in all children with new onset, otherwise unexplained presentations consistent with the effects below, particularly in the presence of constipation and anaemia.

Health effects of severe lead exposure

Haematological

At BLC >1.45 μmol/L (>30 µg/dL):

• anaemia

(Decreased haem synthesis or decreased measures of red blood cell haemoglobin or both have also been reported at BLC<1.45 μmol/L (<30 µg/dL), but in our experience clinically significant anaemia is rarely observed at such low BLCs.)

Gastroenterological

At BLC>1.45 μmol/L (>30 µg/dL):

• colic
• nausea
• vomiting
• diarrhoea
• constipation

Central neurological

At BLC>1.45 μmol/L (>30 µg/dL):

• headache
• altered alertness and activity levels
• ataxia

At BLC>4.83 μmol/L (>100 µg/dL), there is increased likelihood of:

• cerebral oedema
• encephalopathy
• seizures

Peripheral neurological

At BLC >1.45 μmol/L (>30 µg/dL):

• motor and sensory neuropathy

Note: above information taken from the Agency for Toxic Substances and Disease Registry (ATSDR).

At what blood lead concentrations do clinical effects occur?

Although the symptoms and signs described above are often not evident until blood lead concentrations are above 1.45 μmol/L (30 μg/dL), there is increasing evidence that lead has deleterious health effects at blood lead concentrations considerably lower than this. The developing nervous system is particularly susceptible with evidence that BLCs even below 0.24 μmol/L (5 μg/dL) may have deleterious effects on cognitive function and adverse behavioural effects in children. Therefore, there is essentially no BLC in children that is considered safe.

Likely health effects

Acute effects may occur in days if exposure is substantial, but generally exposure is chronic, with health effects developing gradually as body burden increases. Cerebral oedema, encephalopathy or seizures are unlikely to occur at a BLC <4.83 μmol/L (<100 μg/dL).

Two systematic reviews however identified behaviour effects in patients (attention, hyperactivity) at concentrations <0.48 μmol/L (<10 μg/dL) and possibly puberty delay and adverse cognitive effects at <0.24 μmol/L (<5 μg/dL) (1, 2).

What clinicians should do

Taking a clinical history by asking your patient appropriate questions is an essential part of making a diagnosis. This is particularly important when diagnosing lead exposure; your index of suspicion may be raised by the answers you receive.

Clinicians should specifically ask if a child is showing any pica behaviour and should have a particularly low threshold for screening for lead poisoning in children with learning disabilities or behavioural disorders as pica may be harder to identify in these cases. Parents or carers should be directly questioned about risk factors and potential sources of lead exposure noted above.

Clinicians should be aware that they may be contacted by the UKHSA HPTs, when they have patients with BLCs that exceed the public health intervention concentrations. HPTs can also provide public health advice to clinicians and to families. Contact details for HPTs.

Where to obtain expert advice on diagnoses and management

The National Poisons Information Service (NPIS) computerised database, TOXBASE®, is available free of charge to registered NHS users and contains detailed monographs on the diagnosis and management of lead poisoning.

The NPIS 24-hour telephone helpline (0344 892 0111) is available to health professionals for discussion of more complex cases. Where appropriate, senior medical staff can discuss their cases directly with an NPIS consultant clinical toxicologist. Non medics and the public, please call NHS 111.

How to confirm a diagnosis of lead poisoning

A whole blood lead concentration should be undertaken in all cases of suspected lead poisoning. Please be advised that ethylenediamine tetraacetic acid (EDTA) vacutainers should be used for blood collection when measuring BLC.

Blood lead testing can be arranged and paid for by the GP or general hospital. If exposure occurred through an occupational setting, then it is the responsibility of the workplace’s occupational health (OH).

NHS testing for blood lead concentration

Many district general hospitals will have an arrangement with a hospital that does have a laboratory that is fully accredited by the Clinical Pathology Accreditation (CPA) scheme or equivalent body. It should be possible for a BLC requested from any NHS hospital to be available within one week.

If parents or carers provide a BLC undertaken by an external laboratory, it is important to ensure that the laboratory is appropriately accredited.

Other clinical investigations that may be appropriate include:

• full blood count

• iron status (iron stores are generally low due to preferential lead uptake) if anaemia is present

• blood or serum calcium concentration

• abdominal X-ray if accidental non-food item containing lead is suspected

It is important to note that testing of hair, teeth or fingernails for lead, sodium calcium edetate lead-mobilization tests or neurophysiological function tests are not recommended.

Radiographic imaging or X-ray fluorescence of long bones are not part of the routine clinical work-up for suspected lead poisoning in a child. Although abdominal X-rays may be helpful if the suspected source is an ingested non-food item, the X-ray analysis of long bones for growth arrest ‘lead lines’ is not routinely recommended.

Treatment options for lead poisoning in children

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 investigative imagination and persistence, acknowledging the principal sources of exposure outlined above. Remember that the source may be at school, a relative’s or other frequently visited property. Appropriate investigations can be carried out with advice from UKHSA HPT, who will work with local authorities to investigate and offer remediation advice to homeowners or landlords. Contact details for your local HPT.

Management of cases where the blood lead concentration is >0.24 μmol/L (>5 μg/dL) but below 2.4 μmol/L (50 μg/dL) normally involves only removal from exposure, however iron and calcium supplements may decrease both pica and absorption of lead.  Chelation therapy may be considered in some cases of chronic poisoning. Expert advice should be sought in these cases (see details for NPIS).

It is reasonable to offer chelation therapy to children who are symptomatic or have a BLC >2.4 μmol/L (>50 μg/dL), although there is reliable evidence that chelation therapy does not improve cognitive function in children ≤3 years old with BLCs of ≤2.2 μmol/L (≤45 μg/dL).  Chelation is futile however if re-exposure occurs following treatment.

Where chelation therapy is indicated, 2 drugs are available; oral DMSA (succimer) 30 mg/kg/day (DMSA is not licensed in the UK) or sodium calcium edetate 40 mg/kg twice daily (or 75 mg/kg/daily) by IV infusion for 5 days. Expert advice should be sought from NPIS consultant clinical toxicologist before considering either agent.

How to monitor lead levels in children with increased blood lead concentration

This will depend on the initial value and the circumstances.

Where the initial BLC is <2.4 μmol/L (<50 μg/dL), removal from exposure and a repeat measurement of the BLC 4 weeks later is usually all that is required initially. Lead levels do decline slowly in children, and further follow-up will depend on the child’s clinical condition (for example, if pica behaviour is continuing).

If the initial BLC is >2.4 μmol/L (>50 μg/dL), chelation therapy should be considered, after taking expert advice (see above). In these circumstances BLC should be measured immediately before and after treatment and ideally during the chelation course. There is usually a rebound in the BLC following chelation (as lead moves from the bone to blood) so a repeat BLC measurement should be undertaken 1 week after the end of each chelation course.

There may be cases where BLCs are not decreasing as expected following the implementation of interventions to reduce exposure. This could be because not all sources of lead have been identified or the interventions put in place to reduce exposure have not been effective. Therefore, further investigation to ensure all potential sources have been identified and an assessment of the control measures implemented may be required.

The rate at which the BLC falls will be dependent upon the total lead body burden. There is some evidence that lead accumulated in the bone from historical exposures, may be remobilised from bone to blood following implementation of mitigation measures. Therefore, this may mask the effectiveness of the measures. For clinical advice including when to retest the BLC in complex cases contact the NPIS (see contact details above).

Public health interventions

Public health interventions include interruption of lead exposure pathways by source identification and remediation or abatement, and consideration of whether others may be at risk of exposure.

The public health intervention concentration for lead is ≥0.24 μmol/L (≥5 μg/dL) and voluntary notification to UKHSA is recommended for a public health response.

Clinical and public health management of cases

BLC of ≥0.1μmol/L (≥2 μg/dL) to <0.24μmol/L (<5 μg/dL)

Clinical management interventions include:

• identify and remove or abate sources of exposure

• correct calcium and iron deficiency

• repeat BLC testing 4 weeks after removal from exposure

Public health management intervention concentration level is not met and notification not indicated unless concerned about a wider public health risk, for example a cluster of cases or family associated with same exposure source.

BLC of ≥0.24 μmol/L (≥5μg/dL) to < 2.4μmol/L (<50 μg/dL)

Clinical management interventions include:

• identify and remove or abate sources of exposure

• correct calcium and iron deficiency

• repeat BLC testing 4 weeks after removal from exposure

• if symptomatic, discuss with NPIS (as rarely may benefit from chelation)

Voluntary notification to UKHSA is recommended for a public health response (see below).

BLC of ≥2.4 μmol/L (≥50 μg/dL) to <3.3μmol/L (<70 μg/dL) and non-encephalopathic

Clinical management interventions include:

• identify and remove or abate sources of exposure

• correct calcium and iron deficiency

• discuss with NPIS

• consider hospital admission

• consider chelation

• repeat BLC testing 1 week after treatment

Voluntary notification to UKHSA is recommended for a public health response (see below).

BLC of ≥3.3 μmol/L (≥70 μg/dL) or encephalopathic

Clinical management interventions include:

• discuss with NPIS

• identify and remove or abate sources of exposure

• correct calcium and iron deficiency

• admit to High Dependency Unit if encephalopathic

• chelation using dimercaptosuccinic acid (DMSA, succimer), or sodium calcium edetate under expert advice

• monitor BLC according to expert advice

Voluntary notification to UKHSA is recommended for a public health response (see below).

Public health response

Public health interventions include:

• systematic identification of potential exposure sources and pathways by questionnaire and environmental assessment, for example home, school or care settings

• advice on lead source removal or abatement to interrupt exposure pathways

• consideration if other vulnerable individuals (children, pregnant women) at risk

• provide advice on further BLC monitoring following removal from exposure

• surveillance to expedite response, and to describe case epidemiology to inform further public health interventions

Lead exposure in adults

Lead in the workplace

Workplace exposure to lead and inorganic lead compounds may occur in a variety of occupations, including steel welding and spray coating, roofing, battery manufacturing or plumbing.

Employers are required by law to limit the exposure of their workers to lead; this is achieved by regular monitoring of workers BLC and subsequently acting on them if these concentrations are too high.  Employers must comply with the Control of Lead at Work Regulations 2002, and the accompanying Health & Safety Executive (HSE) Approved Code of Practice. These provide requirements for biological testing. It is important to recognise that occupational work which involves lead can lead to exposure in the home if contaminants, for example, dust and paint flakes are brought into the home on dirty work clothing, or if family members have hobbies which involve lead such as stained-glass window making that could expose others in the home.

It has been noted by the HSE, that staff who worked with lead before 2002 may have built up a body burden, and therefore it could take a long time to reduce BLC, and staff may continue to work as long as their BLC is <3.86 μmol/L (<80 μg/dL) and the zinc protoporphyrin (ZPP) level remains lower than 20 μg/g haemoglobin, or the δ-aminolevulinic acid dehydratase (ALAD) level remains greater than 6 European units or the urinary δ-aminolevulinic acid (ALAU) level remains lower than 20 mg/g creatinine.

For these longer-term employees who continue in work under these circumstances, the employer should nevertheless make every effort to reduce the employee’s BLC to below 60 μg/dL, and the doctors should consider increasing the frequency of testing, but suspension from work should occur if health effects (for example anaemia) are exhibited.

Pregnant women

High lead concentrations have also been observed in pregnant women who have eaten painted plaster due to cravings for non-food items. Pregnant women should also avoid the use of traditional medicines and cosmetics, especially where the ingredients are unknown or the products may be unregulated (such as those bought on the internet from an unknown source).

Long-term lead levels

Blood lead concentrations in children may remain elevated 6 to 12 months following implementation of interventions to reduce exposure.

Possible reasons include one or more of the following:

• additional lead exposure sources exist which have not been identified

• mitigation has not been effective

• lead accumulated in the bone from previous exposures has been re-mobilised from bone to blood following implementation of mitigation measures to reduce exposure

In these circumstances a clinical decision can be made to retest after an extended period of time (for example, 6 months).

Learning disabilities and pica in children with elevated blood lead

Learning disabilities are a group of heterogenous conditions that can be classified by different systems both nationally and internationally.

The National Institute of Clinical Excellence (NICE) defines 3 core criteria for diagnosis around:

• lower intellectual ability (usually defined as an IQ of less than 70)

• significant impairment of social or adaptive functioning

• onset in childhood

The severity of learning disability is on a spectrum, ranging from mild to profound and multiple; this is also usually differentiated by measures of intellectual testing.

Pica magnifies the risk of accidental ingestion of toxic substances including lead in children, with elevated blood lead concentrations being a well-recognised complication of the condition. Pica is defined as the eating of non-nutritive, non-food substances, persistent over a period of at least one month, inappropriate to the developmental level of the individual that is not culturally or socially normal. Pica is particularly common in children living in deprivation and with a learning disability (correlates too with severity of learning disability). Not only is there the association between lead exposure and learning disability, there is also the theory of reverse causation in the literature too, postulating that learning disability that is linked with pica correlates with elevated BLCs.

A key message for investigating officers when communicating with families as part of the lead investigation process is around making reasonable adjustments. There should be adjustments in terms of ensuring that information is accessible (suited to an individual’s communication needs, for example easy-read information) and ensuring equity in access, whether this be with communications (longer time-frames for calls, digitally inclusive if virtual, opportunity for appointments in person if needed) or with clinical investigations (longer time-frames for blood-taking appointments, ensuring that family or carers are able to accompany, accessible information in advance).

WHO guideline

The purpose of the WHO Guideline for clinical management of exposure to lead (October 2021) is to assist physicians in making decisions about the diagnosis and treatment of lead exposure for individual patients and in mass poisoning incidents.

The guideline presents evidence-informed recommendations on the:

• interpretation of blood-lead concentrations
• use of gastrointestinal decontamination
• use of a chelating agent
• use of nutritional supplements

Additional information

Interventions

Paper on effectiveness of interventions

WHO lead poison prevention campaign documents

UNICEF report on lead exposure in children

Toxicology

Chemical compendium Lead: Health effects, incident management & toxicology

Committee on Toxicity statement on potential risks from lead in the infant diet

BMJ Case Report: Lead in a case of encephalopathy

BMJ Clinical Updates: Lead exposure in children

BMJ Case Report: Lead in a case of encephalopathy

BMJ Clinical Updates: Lead exposure in children

EFSA Lead dietary exposure in the European Population

CDC Low level Lead exposure harms children: A renewed call of primary prevention

Population

WHO: 10 chemicals of major public health concern

WHO lead (including exposure to lead, batteries, paint and BL testing)

UKTIS Lead in pregnancy monograph

BUMPS leaflets for pregnant women on lead

Lead Exposure in children Surveillance System: surveillance reports (from 2021)

Unusual cases of lead poisoning in the UK: Chemical Hazards and Poisons report No 26

US Preventive Services Task Force Screening for elevated blood lead levels in children:

• recommendation

• full evidence review

Occupational exposure to lead

The Control of Lead at Work Regulations 2002

HSE: Control of Lead at Work Approved Code of Practice L132

HSE: Working safely with lead

HSE: Lead and you

References

1. US National Toxicology Program (NTTP). ‘NTP Monograph on Health Effects of Low-Level Lead’ 2012: US Department of Health and Human Services

2. US Environmental Protection Agency. ‘Integrated Science Assessment for Lead’ National Center for Environmental Assessment 2012