LEAD Action News
LEAD Action News Volume 14 Number 1, October  2013, ISSN 1324-6011
Incorporating Lead Aware Times ( ISSN 1440-4966) and Lead Advisory Service News (ISSN 1440-0561)
The Journal of The LEAD (Lead Education and Abatement Design) Group Inc.
Editor-in-Chief: Elizabeth O’Brien, Editorial Team: Hitesh Lohani, Anne Roberts and David Ratcliffe

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The full story: The only safe level of lead exposure is zero

Authors:
Mark Patrick Taylor, Professor of Environmental Science, Faculty of Science, Macquarie University, Sydney, NSW, Australia.

Chris Winder - Professor of Occupational Health, Safety and Environmental Management, Australian Catholic University, Sydney, NSW, Australia.

Bruce Lanphear - Professor of Children’s Environmental Health,
BC Children’s Hospital, Simon Fraser University,
Vancouver, British Columbia, Canada.

[Editors’ note: A shorter version of this article was published as a Lead Opinion Piece, titled “There is no safe level of lead exposure”, ABC Online Environment, at http://www.abc.net.au/environment/articles/2013/10/15/3868663.htm - 15th October 2013.]

In about 1960, health agencies in Europe and the USA set, and then lowered (as more evidence became available) a blood lead “level of concern” from 60 μg/dL, to 40 μg/dL (in 1971), to 30 μg/dL in 1985, and lastly, to 10 μg/dL in 1991. This was the level that pediatricians and other health professionals could use for establishing priorities and interventions for a lead poisoned child (see Figure 1). In 2009, Germany lowered the reference value for child (aged 3-14 years) blood lead levels to 3.5 μg/dL [http://www.sciencedirect.com/science/article/pii/S1438463911000794] and in 2012, the US CDC eliminated the “level of concern” set at 10 μg/dL and established 5 μg/dL as the intervention (reference) level for individual children [http://www.cdc.gov/nceh/lead/ACCLPP/CDC_Response_Lead_Exposure_Recs.pdf].  

Changes to the blood lead level of ‘concern’ over the last 50 years

Figure 1: Changes to the blood lead level of ‘concern’ over the last 50 years.

In 1993, Australia’s current blood lead goal of 10 µg/dL was revised downwards from the 1983 level of 25 µg/dL, which mirrored the blood lead level established by the US Centers for Disease Control (CDC) in 1991. The figure of 10 µg/dL was reaffirmed by the National Health and Medical Research Council (NHMRC) after a review in 2009 [http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/gp2-lead-info-paper.pdf]. This review concluded that “The nature of the ‘dose-response’ relationship between lead exposure and children’s intellectual abilities and behaviour is also contentious.” Importantly however, the NHMRC also noted in their Information paper that “No threshold of lead exposure below which any exposure might be considered ‘safe’ in respect of cognitive abilities has ever been identified.”

To date, the majority of research on the neurocognitive and behavioural effects of lead exposure has been conducted in the US, with very few studies examining the impacts and long-term outcomes in Australian populations in terms of school performances or criminality. The majority of Australian published research was conducted in the 1990s and was based on Port Pirie children, who had higher lead levels from smelter emissions than are typically found today either there or elsewhere. However, Rachel Earl’s 2011 PhD study [http://digital.library.adelaide.edu.au/dspace/bitstream/2440/71322/1/02whole.pdf] investigated the effects of low-level lead exposure on 106 children (whose mean blood lead concentration was 4.97 µg/dL) from Port Pirie and Broken Hill. Her study drew the same conclusions as previous international studies: [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257652/] that there was no safe, lower threshold for lead exposure [http://digital.library.adelaide.edu.au/dspace/handle/2440/71322]. Importantly, the study’s findings confirmed that low and initial lead exposures may indeed cause proportionately greater impact on children’s cognition than higher levels. 

Photographer: Hugh O’Brien. Title: Playground In Shadow Of Lead Smelter, Mt Isa, Queensland. Graphic: Entry in the Volcano Art Prize 2013. Photographer: Hugh O’Brien. Title: Playground In Shadow Of Lead Smelter, Mt Isa, Queensland. Lead-safety message: Check the wind direction before playing in this park. http://volcanoartprize.com/portfolio-item/obrien
-hugh-playground-in-shadow-of-lead-smelter-
mt-isa-queensland/

In short, this means that prevention of any lead exposure must be a key goal of any public policy or approach to lead exposure risks and that the de facto goal of only aiming to keep children’s blood lead below 10 µg/dL (Port Pirie - http://thumbsupforlowlevels.com/about-us/aims; Mount Isa - http://www.livingwithlead.com.au/about-lead/; Broken Hill - http://www.fwlhn.health.nsw.gov.au/UserFiles/files/FAR%20WEST%20Lead%20Health%20
Data%20Report%202011.pdf
) is outdated and will inevitably result in detrimental exposures. We have already argued for the effective elimination of exposures [http://www.mq.edu.au/pubstatic/public/download.jsp?id=71937] because as the NHMRC and others have argued, there is no safe lower level.

The evidence against the argument that the nature of the dose-response effect is “contentious” is now so overwhelming that it is no longer contentious, except to the most biased, and it is self-evident that Australia needs to respond quickly, especially to protect children. We have argued in recent articles in the Medical Journal of Australia [https://www.mja.com.au/journal/2012/197/9/eliminating-childhood-lead-toxicity-australia
-call-lower-intervention-level?0=ip_login_no_cache%3Dcfca1c55fe4ab5b3b391d9591bec525a
] and elsewhere [http://theconversation.com/time-to-rethink-blood-lead-goals-to-reduce-risk-to-childrens-health-10493], that the current goal is too high and that effective elimination of blood lead exposures is an urgent goal that health and environmental authorities must seek to attain. Effective elimination means that we should aim for children to have blood lead levels below 1 µg/dL. Natural levels of lead in blood were calculated two decades ago at 625 times less than the current Australian “maximum” (the NHMRC goal to be below, of 10 µg/dL) [http://www.nejm.org/doi/full/10.1056/NEJM199205073261916].

The effects and absorption of lead exposure are non-trivial and are lifelong

The United States Environmental Protection Agency (US EPA) 2013 Integrated Science Assessment for Lead [http://www.epa.gov/ncea/isa/lead.htm] concluded that the weight of evidence shows adverse cognitive function effects of lead exposure on populations of children down to 2 µg/dL, the effects of which may be irreversible and persist into adulthood.

Lead exposure is associated with delayed pubertal onset and adverse reproductive and development effects in young adults who have mean blood levels less than or equal to 5 µg/dL. Adults are not protected from exposures either, causal relationships having been shown to exist between low-lead exposures (< 10 µg/dL) and adverse cardiovascular effects (e.g. increased blood pressure, hypertension, coronary disease). In addition the US EPA concluded that there was a likely causal relationship between lead exposure and reduced kidney function, all which are considered to reduce lifespan and quality. Toxicological evidence also provides strong evidence that lead exposure reduces male semen quality and may affect some aspects of female reproductive function. Finally, the US EPA concluded that the evidence supports a likely causal relationship between high levels of lead exposure and cancer.

All of these (and more) exposure effects may be confounded by a myriad of other social, economic, genetic and environmental factors. However, the US EPA’s findings are supported by the conclusions reached in other major international review’s of research into the effects of low-level lead exposures (Canada, Germany, USA, WHO) [http://hc-sc.gc.ca/ewh-semt/pubs/contaminants/dhhssrl-rpecscepsh/index-eng.php; http://www.sciencedirect.com/science/article/pii/S1438463911000794 http://ntp.niehs.nih.gov/go/36443; http://www.who.int/ceh/publications/leadguidance.pdf]. As a result, there have been worldwide recommendations to reduce lead exposures.

In 2012, the globally respected United States Centers for Disease Control stopped using a blood lead level 10 µg/dL as a “level of concern” and is now using a reference value of 5 µg/dL to identify children who have been exposed to lead and who require case management. Such an approach in Australia is likely to mean more than at least 50 % of the children under 5 years of age in Broken Hill, Mount Isa and Port Pirie would need greater protection and intervention.

Photographer: Julia Wyllie. Title: Getting the lead out.Graphic: entry in Volcano Art Prize 2013. Photographer: Julia Wyllie. Title: Getting the lead out. Lead-Safety Message: Silent blanket of lead dust falls over Broken Hill.

Although national blood lead values are falling in major cities and mining towns (Figure 2), the quiet concern about lead exposure is very clearly evident in Medicare statistics that show 107,810 blood lead tests were conducted on all Australians in the last decade [https://www.medicareaustralia.gov.au/cgi-bin/broker.exe?_PROGRAM=sas.mbs_item_standard
_report.sas&_SERVICE=default&DRILL=ag&_DEBUG=0&group=66665&VAR=services&STAT=
count&RPT_FMT=by+state&PTYPE=finyear&START_DT=200307&END_DT=201308
]. It is an unfortunate and a significant lost opportunity that the results from these tests are not captured, stored and analyzed by the NHMRC as part of its statutory work - the work to raise the standard of individual and public health throughout Australia.  In the absence of collation and analysis of such raw data or a national blood lead survey of all ages (as have been regularly carried out in the USA since 1976), we used USA population lead survey data to estimate that ~ 100,000 Australian children under five years of age may have blood lead levels > 5 µg/dL, which are likely to cause adverse health effects [https://www.mja.com.au/journal/2012/197/9/eliminating-childhood-lead-toxicity-australia
-call-lower-intervention-level?0=ip_login_no_cache%3Dcfca1c55fe4ab5b3b391d9591bec525a
].

Changes in blood lead levels in Australian Children between 1990-2010

Figure 2: Changes in blood lead levels in Australian Children between 1990-2010. Note, that the data contains arithmetic and geometric mean values (as reported in the studies) and in some cases data was collected over more than one calendar year. Most of the data points relate to children under the age of 5. In the only national blood lead study, only children aged 12-48 months were tested.

Lead exposure from soils and dusts in Australian communities is dominated by three sources: (i) mining and smelting emissions, (ii) lead paint and (iii) leaded petrol. In mining affected areas, the original contaminant load is sourced primarily from smelter fallout, dust from spoil heaps or tailings that have been transported deliberately or inadvertently into and dispersed across human and natural environments. The release of such contaminants can pose a significant potential environmental and human health threat to people living, working and recreating in or near to such environments. Lead levels in paint were up to 50% by weight before the 1950s but thereafter several reductions were mandated bringing the allowable concentration to 0.1% in 1997 [http://www.environment.gov.au/atmosphere/airquality/publications/housepaint.html].

Unleaded petrol for road vehicles was introduced in Australia in 1985, with the lead content of petrol declining from 0.84 g/L in 1990 to 0.2 g/L in 1996, until it was finally banned in 2002 http://www.environment.gov.au/atmosphere/airquality/publications/qa.html]. The consequences of the use of lead in petrol on environmental quality have been significant. In two national assessments of petrol lead emissions 3,842 tonnes of lead were emitted in Australian capital cities in 1976 [ http://catalogue.nla.gov.au/Record/2270078 and 2,388 tonnes of lead were emitted in 1985 [ http://catalogue.nla.gov.au/Record/1973311], despite mandated reductions of allowable lead in petrol. As a result, many of the older, larger inner city areas of Australia became heavily contaminated with lead [http://link.springer.com/article/10.1007/s11270-010-0411-3?LI=true; http://link.springer.com/article/10.1007/s11270-010-0555-1?LI=true; http://www.sciencedirect.com/science/article/pii/S0269749110003738) and it is these sources that continue to expose children to potentially adverse levels of environmental lead (http://www.sciencedirect.com/science/article/pii/S0269749113004661). In contrast, smaller rural towns with significantly lower vehicle use and population densities, and no mining and smelting industries are likely to have a less significant legacy of environmental lead exposure (http://www.sciencedirect.com/science/article/pii/S0883292713001637), except in older housing were lead paint was used or where the source of drinking water is rainwater, river water or groundwater which has not been tested for lead.

Although Australia continues to be a world leader in lead metal mining, smelting and processing there has been a significant lack of research funding directed towards understanding exposures and the real risks they play. For example, there has never been any major longitudinal study investigating environmental lead plus other metals exposures in Mount Isa or Broken Hill, despite their importance in the Australian landscape and the current and historic childhood (and occupational) lead exposures. Any negative human health impact arising from lead extraction and refining has been down-played consistently by mining companies, governments, councils, health officials and regulators so as to not challenge the status quo and disrupt economic opportunities for remote rural Australian towns and the wider Australian community [http://onlinelibrary.wiley.com/doi/10.1111/j.1440-1754.2010.01777.x/full; http://www.tandfonline.com/doi/abs/10.1080/19338240903338189#.UlPK8ih0qS0].

Photographer: Katie Mortimer. Title: Irremovable Reminders.Consequently, affected communities have never been able to assess the real risk to their health because of the systematic obfuscation of the facts in regard to the source of any potentially related environmental health problem [ http://theconversation.com/lead-poisoning-of-port-pirie-children-a-long-history-of-looking-the-other-way-8296; http://www.sciencedirect.com/science/article/pii/S0269749113002455]. As a result, generations of families have been unable to make informed choices about the nature and quality of the environment in which they reside or work. Consequently, as a result of ignorance, misinformation and deliberate down-playing of the evidence, communities residing adjacent to lead mining, smelting and refining centres such as those in Broken Hill, Port Pirie and Mount Isa continue to be exposed to environmental lead, a known neurotoxic contaminant.

Graphic: entry in Volcano Art Prize 2013. Photographer: Katie Mortimer. Title: Irremovable Reminders. Lead-Safety Message: Years of mining in Broken Hill has caused widespread lead contamination. Despite the blatant reminders throughout the town of the strong mining history, such as this slag the town is centred around, residents are ignorant of issues associated with the high levels of lead present. Action is greatly needed for a lead free future in Broken Hill.

Finally, with the overwhelming mountain of evidence that Australia’s lead level for children is too high, we ask why would it take the NHMRC so long (2012-2014) to undertake what appears to be a review of reviews [ http://www.nhmrc.gov.au/guidelines/publications/new36new37 ], in the anticipation that they might conclude something different from other global experts?

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