Lead absorption notification levels have reduced

Lead is a common environmental pollutant

Lead is a common and persistent pollutant found in a variety of environmental and occupational sources (Table 1).^{1, 2} Following the removal of lead from petrol in 1996, the most common source of exposure in New Zealand is from lead-based paint used in pre-1980s houses (particularly those built before 1945).³ The primary routes through which lead enters the body are ingestion or inhalation.² It is estimated that 50% of the lead deposited in the respiratory tract is subsequently absorbed into the systemic circulation, whereas 5–15% of ingested lead is absorbed through the gastrointestinal mucosa.²

Once lead enters the blood, it acts as a cumulative toxicant, building up progressively in various body systems following each exposure event, e.g. brain, kidney, liver and bones.⁴ In pregnant females, lead can cross the placenta to the developing fetus, which may result in miscarriage, stillbirth, premature birth or low birth weight.² Approximately 70–95% of absorbed lead is deposited in bones; given that the half-life of lead is decades, this can serve as a reservoir for re-release into systemic circulation and soft tissues over time.² The mobilisation of lead from bones may increase in response to specific biological processes, e.g. pregnancy and menopause.⁴ As such, people may present with various symptoms depending on the magnitude or duration of exposure, and their individual characteristics, e.g. age, co-morbidities (see: “Assessing potential cases of lead exposure in primary care”).⁵

Table 1. Environmental sources of lead and risk factors for exposure.^{1, 4}

Lead exposure and absorption in New Zealand

Due to the public health implications associated with environmental exposure, lead absorption is a notifiable condition if blood levels are greater than a certain threshold (see: “Reporting of notifiable lead absorption”). In 2019, the notification rate for lead absorption in New Zealand was 5.0 per 100,000 population (204 total), double the rate in 2017.^{* 6} This increase was predominantly due to higher numbers of adult notifications, with rates of elevated blood levels in children aged 0–14 years remaining relatively consistent since the early 2000s.⁶

Since 2014, notifiable rates of lead absorption have been consistently higher in:⁶

• People aged 45–64 years
• Pacific peoples
• People living in low socioeconomic areas
• Males

Occupational exposure. Painters are consistently the occupational group with the most lead absorption notifications in New Zealand, accounting for approximately 40% of work-related cases in 2019.⁶ Other high ranking groups include metal workers and those working in radiator repair.⁶

Non-occupational exposure. The most common sources of non-occupational lead exposure are lead-based paints, indoor rifle ranges, bullet/sinker manufacturing, or unknown causes.⁶ Levels of lead absorption are generally lower in people with non-occupational exposure; in 2019 the levels in reported cases ranged from 0.48–0.71 micromol/L.⁶

^*N.B. The statistics presented in this section are based on a blood lead notification threshold of ≥0.48 micromol/L, which has since been lowered (for more information, see: “On 9 April, 2021, the lead absorption notification level reduced”). As a result, there likely would have been many cases of lead absorption which were not reported that would qualify as notifiable cases now.

Assessing potential cases of lead exposure in primary care

Investigating people with potential lead exposure. In general, symptoms of lead poisoning do not appear immediately after exposure.⁵ However, people without any presenting features will sometimes seek primary care evaluation due to concern over a recent lead exposure event, e.g. a community exposure. In such cases, it is important to identify the potential source, the quantity of lead potentially consumed, and the chronicity of exposure.⁵ If there is significant clinical concern over the exposure event, then it is reasonable to request a blood lead level test, particularly in children, females of childbearing age, pregnant females, or in people with a household member who has recently tested positive for raised lead levels.

Investigating symptomatic people. In very rare cases, people may present with symptoms of lead poisoning following several days, weeks or even months of sustained exposure, yet be unaware that lead is the potential cause.⁵ Early symptoms are generally non-specific, predominantly affecting the gastrointestinal tract and nervous system:⁴

• Possible gastrointestinal symptoms: reduced appetite, nausea, diarrhoea or constipation, weight loss and stomach pain
• Possible neurological symptoms: headaches, mood disturbances (e.g. irritability or depression), memory impairment and tingling/numbness in the fingers and hands; in severe cases, lead-induced toxicity may present as encephalopathy, i.e. the patient may exhibit an altered mental state – if this is suspected, request an emergency assessment in secondary care.
• Constitutional symptoms: excessive fatigue, decreased libido, sleep disturbances

Identifying lead as the possible cause of symptoms in this scenario can be very challenging. Lead poisoning may be suspected early as the cause based on the patient’s history – including employment and hobbies – or become apparent later as a possible cause after differential diagnoses have been excluded. For parents of young children with suspected lead poisoning, it can be useful to ask questions such as:

• Does your child frequently put non-edible objects in their mouth?
• Do they suck their thumb or bite their nails?
• Do they have an old painted cot or any old painted toys?

Monitoring people at high risk. For people with higher-risk occupations, e.g. painting contractors (including self-employed), blood lead level surveillance may be considered a routine requirement under the Health and Safety at Work Act 2015.³ The frequency of testing is guided by employment-specific exposure characteristics, and “should be determined by an occupational health nurse or other suitably qualified medical professional”.³

^{Testing blood lead levels if symptoms or history indicate lead poisoning is possible}

Testing for raised blood lead levels can support a diagnosis of lead poisoning and should be requested if there is clinical suspicion of lead poisoning based on the patient’s history and/or symptoms.

If blood lead levels are tested, also consider requesting:²

• Complete blood count – anaemia is common in patients with lead poisoning
• Renal and liver function testing – accumulated lead may adversely affect the function of these organs; given that kidneys are the primary route for lead excretion, renal dysfunction may be a contributing factor to chronic lead toxicity in some cases

Despite its importance in evaluating patients with suspected lead poisoning, clinicians should recognise that blood lead testing is a measure of recent absorption and therefore reflects acute exposure events (i.e. within the past three to four weeks).⁴ Lead stored in bone, teeth and organs which has accumulated over long periods of time will not be detected with this approach.⁵ Testing is also unlikely to be completely diagnostic in isolation, particularly for neurodevelopmental delays in children that can have a myriad of causes.⁴

Reporting of notifiable lead absorption

There is no known safe level of lead exposure. Under the Health Act 1956 and the Hazardous Substances and New Organisms Act 1996, cases of injury or disease caused by exposure to lead must be notified to a Medical Officer of Health, who will subsequently assess the information about the exposure and determine if further follow-up is required.⁸ For lead absorption, suspicion based on symptoms and history alone is insufficient for notification; a confirmed blood test is required with the result meeting a certain threshold value.

On 9 April, 2021, the lead absorption notification level reduced

In 2007, the notifiable blood level for child or non-occupational adult lead absorption in New Zealand was lowered from 0.72 micromol/L to 0.48 micromol/L due to mounting evidence that lower blood lead concentrations were associated with an unacceptable risk of adverse effects.⁶ On 9 April, 2021, the level at which blood lead absorption becomes notifiable under the Health Act 1956 was reduced even further to 0.24 micromol/L (5 micrograms/dl).^{9, 10} This change is consistent with the reference value recommended by the Centers for Disease Control and Prevention (CDC) in the United States and the Australian National Health and Medical Research Council.⁴

Clinicians can report notifiable lead absorption electronically

In general, notifiable lead exposure will be reported directly to a Medical Officer of Health by the community laboratory performing the test. However, the information provided in these reports is limited. Clinicians in primary care are therefore encouraged to also submit a Hazardous Substances Notification form to their Public Health Unit to provide additional information, which can facilitate accurate identification of the exposure source, leading to controls being put in place to prevent further public health issues. In addition, the Public Health Unit will submit notifications to the national Hazardous Substances Surveillance System, with identifiable data removed, which:¹³

• Helps to further describe the epidemiology of lead exposure in New Zealand
• Informs policy development to improve monitoring and response strategies

BPAC Clinical Solutions, in association with Environmental Health Intelligence New Zealand, and sponsored by the Ministry of Health, have developed a Hazardous Substances Disease and Injury Reporting Tool (HSDIRT), that permits electronic reporting of all hazardous substance exposures, including lead (Figure 1).¹³ It is available via Medtech, Indici, MyPractice and Profile patient management systems.¹³

To access HSDIRT, go to the bestpractice Decision Support dashboard in your patient management system:

• Look for “Module List”
• Expand the “Hazardous Substances & Lead Notifications” tab
• Click on “Hazardous Subs & Lead Notifications” (N.B. ticking the green box will add the module to your “Favourites”)

If your practice does not have access to this tool and you want to make a notification, phone your Public Health Unit directly. The staff will enter the case information into a HSDIRT notification form on your behalf.¹³ If the patient is pregnant, their lead maternity carer should also be advised.

For a walkthrough video explaining how to access and complete HSDIRT notification forms, see: https://vimeo.com/359445622

If you want the HSDIRT tool installed at your practice, contact BPAC Clinical Solutions:

Phone: 0800 633 236
Email: info@bpacsolutions.com
Website contact form: https://bpacsolutions.co.nz/contact/

For further information on hazardous substances disease and injury notifications, see:

• https://bpac.org.nz/BPJ/2016/May/e-notification.aspx
• https://www.ehinz.ac.nz/our-projects/hazardous-substances/hsdirt-notification-tool/

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Figure 1. An example of reporting lead absorption through the Hazardous Substances Disease & Injury Reporting Tool (HSDIRT; lead absorption section denoted in red box).

Follow-up and management of patients with lead poisoning

The Public Health Unit will provide advice on appropriate management and follow-up once a lead absorption notification is received.⁴ In addition, they will direct remediation efforts to ensure that continued exposure to the source of lead is prevented for non-occupational exposure, or contact WorkSafe New Zealand for work-related incidents.⁴

All patients should be provided with education about reducing the risk of future exposure regardless of their blood lead level, i.e. avoiding the likely source(s).⁴ A follow-up blood lead level test should be scheduled (as advised by the Public Health Unit) after the source of exposure has been remediated, and family members should be tested as appropriate – particularly females who are pregnant and children aged under five years.⁴ If a decrease in blood lead levels does not occur, the Public Health Unit should be contacted for further advice.

In rare instances, patients may have a very high blood level or severe symptoms that require immediate chelation treatment in secondary care, e.g. with oral DMSA (dimercaptosuccinic acid). Chelation is usually only recommended for patients with blood lead levels greater than 2.17 micromol/L.^{4, 5} The Public Health Unit will advise on the need for referral to secondary care on a case-by-case basis, however, it is usually required:⁴

• In children or adolescents with blood lead levels greater than 0.72 micromol/L (paediatric advice or assessment)
• In pregnant females with blood lead levels greater than 2.17 micromol/L (acute obstetric assessment)
• In any adult with blood lead levels greater than 3.4 micromol/L (acute medical assessment)

For specific information on management, referral and follow-up in patients exposed to lead, see: https://www.health.govt.nz/publication/environmental-case-management-lead-exposed-persons

For patient information on lead poisoning and reducing the risk of exposure, see: https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/lead-poisoning