Working with Lead

By Rosalind Harrison, Toxicologist, Environmental Health Unit, Department of Health and Human Services, in collaboration with Chrissie Pickin, Deputy Director of Public Health, Tasmania

The concerns raised by the Toxic Heavy Metals Taskforce (The LEAD Group 2010) have opened up various debates relating to heavy metals exposure. Among the issues in the spotlight is the matter of occupational exposure to lead.

Although there are workplace standards for lead exposure in the workplace, it is accepted that blood lead levels of workers can be higher than those of the general population.

So, is it now time to revisit, and possibly, revise those standards?

The fact is that working with lead can affect your health. There is a range of lead-risk jobs which can put you at risk of exposure. These include stripping of old lead-based paints, scrap-processing, manufacture of lead-acid batteries, soldering, smelting, and refining.

For anyone who could be exposed to lead or any lead compounds in the workplace, particularly by breathing in or ingesting dust/fumes, employers are required to take certain steps to protect your health, e.g.:

Tell you about the health risks of working with lead;

• Check your health through a blood sample to measure the amount of lead it contains;
• Measure the level of lead in the workplace air;
• Introduce control systems or protective equipment to prevent or control exposure to lead; and
• Provide washing and changing facilities.

In this country, Safe Work Australia has agreed national standards and codes of practice for the control and safe use of lead at work (Safe Work Australia 1994a and 1994b). These documents detail the requirements for biological monitoring – this is measuring the concentration of lead in blood and is reported as micrograms (µg) of lead per decilitre (dL) of blood. Biological monitoring gives a good indication of how much lead has been absorbed by inhalation and ingestion. Medical examinations are also carried out.

In Australia, the frequency of biological monitoring depends on the most recent blood lead level and the reproductive age of the individual (Safe Work Australia 1994 a and 1994b). For example, all men and women not of reproductive age will be tested every six months, provided that their blood lead level remains less than 30 µg/dL. Women of reproductive age will be tested every three months, provided that their blood lead level remains less than 10 µg/dL. If levels exceed these figures, then more frequent testing is required. To protect susceptible groups of people, certain individuals can be excluded from working in lead-risk jobs; for example, individuals with certain medical conditions, such as anaemia or kidney dysfunction. Similarly, individuals can be removed from lead-risk jobs if their blood lead level becomes too high. A person is removed if they have a blood lead level of 50 µg/dL (all men and women not of reproductive age), 20 µg/dL (women of reproductive age), and 15 µg/dL (women who are pregnant or breastfeeding). The unborn baby and infants are more susceptible to the health effects of lead than adults (NHMRC 2009a), hence the need for greater protections for pregnant and breastfeeding women in the workplace.

Around the world, the situation is similar – blood lead levels are checked regularly and individuals can be removed from their jobs if their blood lead levels are too high. In the UK, medical removal occurs at 60 µg/dL (HSE 2002) and in the US, it occurs at 50 µg/dL (averaged over six months) or 60 µg/dL (OSHA 2008), for general employees (i.e. all men and women not of reproductive age). You will not be allowed to return to a lead-risk job until a medical practitioner considers it safe for you to do so.

Based on the scientific evidence on the effects of low-level exposure to lead, it is not possible to make a definitive statement on what constitutes a ‘safe level’ for blood lead concentrations. This is the view of the National Health and Medical Research Council (NHMRC) as well as other international organisations. The NHMRC makes a number of recommendations on lead exposure (NHMRC 2009a and 2009b):

• All Australians should have a blood lead level below 10 µg/dL;
• All children’s exposure to lead should be minimised; and
• All women are advised to minimise their exposure to lead both before and during pregnancy and also while breastfeeding.

The general population’s exposure to lead has decreased dramatically since the 1970s. The decline in average blood lead levels in the general population can be attributed not only to the removal of lead from petrol, but also to programs and monitoring aimed at reducing lead exposure, and other lead-reduction programs (e.g. the phase out of lead-based paints, eliminating lead in food cans, and the replacement of lead water pipes). The Australian Government phased out the use of lead in petrol in 2002 (NICNAS 2003). Although international studies have demonstrated a decline in children’s blood lead levels associated with the elimination of lead in petrol (Hwang et al 2004, Senanayake et al 2004, Schwemberger et al 2005), there is little Australian data in urban environments unrelated to the lead industry. The only nationwide survey of blood lead concentrations in children was conducted in 1995 - the mean blood lead level in 1-4 year old children across Australia was found to be 5.1 µg/dL (Donovan 1996). There has been no follow-up to this national children’s blood lead survey. A more recent four-year study in Sydney children (aged 6-31 months at recruitment) showed a mean blood lead level of 3.1 µg/dL (Gulson et al 2006, NHMRC 2009b). A two-phase study in pre-schoolers living in Fremantle showed a decline in mean blood lead levels between 1993 (6.82 µg/dL) and 2005 (1.83 µg/dL), which the authors concluded likely to be associated with the phasing out of leaded petrol (Willis et al 1995, Guttinger et al 2008).

Recent scientific research has shown that levels of lead which were once thought harmless can now result in adverse health effects (WHO 2000, ATSDR 2007). There is, therefore, a potential concern that the current lead standards allow workers to be exposed to lead at levels now known to be harmful. The Occupational Lead Poisoning Prevention Program is a program in the US which helps prevent lead poisoning in the workplace. Because of the concern regarding low levels of lead exposure, this program recommends removal from lead exposure if (OLPPP 2009):

• Blood lead level is greater than or equal to 30 µg/dL; or
• Two consecutive blood lead levels (taken one month apart) are greater than or equal to 20 µg/dL.

The program goes on to recommend that a return to any lead-risk job should not be considered until two consecutive blood lead levels (taken one month apart) are less than 15 µg/dL (more stringent exposures are recommended for women of reproductive age).

Everyone is exposed to some lead through its natural occurrence in the environment, and its presence in food and drinking water. However, in the workplace, individuals with lead-risk jobs can be exposed to much greater levels of lead than the general population. These days, the workplace can provide the most potential for exposure. Despite workplace guidelines which are in place to protect the health of workers, it could be argued that exposure in the workplace is high, compared with that in the general population and the recommendations of the NHMRC. Perhaps it is now time to focus our attention on lead exposure in the workplace and consider reducing workers’ blood lead levels to that of the general population.

References

1. ATSDR (Agency for Toxic Substances and Disease Registry) (2007) Toxicological profile for lead
2. Donovan, J. (1996) Lead in Australian children: Report on the national survey of lead in children Australian Institute of Health & Welfare.
3. Gulson, B; Mizon, K; Taylor, A; Korsch, M; Stauber, J; Davis, M; Louie, H; Wu, M; Swan, H. (2006) Changes in manganese and lead in the environment and young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl in gasoline - preliminary results Environmental Research (100) 100-114.
4. Guttinger, R; Pascoe, E; Rossie, E; Kotecha, R; Willis, F. (2008) The Fremantle lead study part 2 Journal of Paediatrics and Child Health (44) 722-726.
5. HSE (Health and Safety Executive) (2002) Control of lead at work (Third edition) Control of Lead at Work Regulations 2002 Approved Code of Practice and guidance 
6. Hwang, YH; Ko, Y; Chiang, CD; Hsu, SP; Lee, CH; Chiou, CH;, Wang, JD; Chuang, HY. (2004) Transition of cord blood lead level, 1985-2002, in the Taipei area and its determinants after the cease of leaded gasoline use Environmental Research 96(3) 274-282.
7. NHMRC (National Health and Medical Research Council) (2009a) Blood lead levels: lead exposure and health effects in Australia NHMRC Public Statement August 2009 
8. NHMRC (National Health and Medical Research Council) (2009b) Blood lead levels for Australians NHMRC Information Paper August 2009 
9. NICNAS (National Industrial Chemicals Notification and Assessment Scheme) (2003) Methylcyclopentadienyl manganese tricarbonyl (MMT) Priority Existing Chemical Assessment Report No. 24, NICNAS, Sydney, NSW 
10. OLPPP (Occupational Lead Poisoning Prevention Program) (2009) Medical guidelines for the lead-exposed worker California Department of Public Health 
11. OSHA (Occupational Safety & Health Administration) (2008) 1910.1025 Lead PART 1910 Occupational Safety and Health Standards, Subpart Z – Toxic and Hazardous Substances 
12. Safe Work Australia (1994a) National Standard for the Control of Inorganic Lead at Work [NOHSC: 1012(1994)] 
13. Safe Work Australia (1994b) National Code of Practice for the Safe Use of Inorganic Lead at Work [NOHSC: 2015(1994)] 
14. Schwemberger, JG; Mosby, JE; Doa, MJ; Jacobs, DE; Ashley, PJ; Brody, DJ; Brown, MJ; Jones, RL; Homa, D. (2005) Blood lead levels – United States, 1999-2002 MMWR CDC Surveillance Summaries 54(20) 513-516 
15. Senanayake, MP; Rodrigo, MD; Malkanthi, R. (2004) Blood lead levels of children before and after introduction of unleaded petrol Ceylon Medical Journal 49(2) 60-61.
16. The LEAD Group (2010) Heavy metal poisoning in an Australian lead mining town – the view from the trenches LEAD Action NEWS 10(4) 1-25 
17. Willis, FR; Rossi, E; Bulsara, M; Slattery, MJ. (1995) The Fremantle lead study Journal of Paediatrics and Child Health 31(4) 326-331.
18. WHO (World Health Organization) (2000) Safety evaluation of certain food additives and contaminants WHO Food Additive Series, No 44: Lead International Programme on Chemical Safety www.inchem.org/documents/jecfa/jecmono/v44jec12.htm