Lead: Part 1

Having highlighted a recent paper on the presence of Lead in game, I have decided to commence a series of specialised ‘limelights’ on the effects of Lead bullets/pellets in humans as a result of game hunting. However, before I address my assignment, I shall first provide a succinct background on Lead’s toxicity.

Inception
For thousands of years, Lead has been widely extracted and used by mankind, mainly due to the availability of its many ores as well as its malleability. In fact, Lead used to be the second most used metal (after Iron).

Lead’s toxicity
Despite its many benefits, Lead’s detrimental effects of morbidity and mortality in humans and animals have been demonstrated by numerous studies. These vary from mild manifestations (such as fatigue, emotional irritability, and insomnia) to the fatal conclusion of death. Published studies have established the following:
- reduced somatic growth (Hauser et al, 2008)
- impaired motor function (Cecil et al, 2008)
- decreased brain volume (Cecil et al, 2008)
- permanent cognitive damage, attention and behavioural dysfunction/problems, impaired cognitive function (Needleman et al, 2002; Canfield et al, 2003; Lanphear et al, 2005; Braun et al, 2006; Schnaas et al, 2006; Cecil et al, 2008; Jusko et al, 2008; Wright et al, 2008)
- reproductive damage, including spontaneous abortion (Borja-Aburto et al, 1999)
- nephropathy (Ekong et al, 2006)
- cancer and cardiovascular disease (Lustberg and Silbergeld, 2002; Menke et al, 2006)
- and even criminal behavior (Needleman et al, 2002; Wright et al, 2008).

A great danger of Lead toxicity is that the symptoms may lag physiological changes, i.e. the affected individual may remain unaware of the danger (similar to the effect of cholesterol). Lead in the blood does not excrete and a major proportion sequesters in soft tissues and bone from where it may be switched on especially during pregnancy (Tellez-Rojo et al, 2004) or old age (Schwartz and Stewart, 2007).

Over the past 50 years, as a result of new studies revealing the toxic effects of Lead at lower levels, the benchmark levels have declined (60 μg/dL in 1960; 25 μg/dL in 1985; and, 10 μg/dL in 1991) (Needleman, 2004). And although the current CDC benchmark level is 10 μg/dL, the published studies indicate that it would be inane to consider even a trifling level of Lead exposure as being harmless (Bellinger and Bellinger, 2006)- for instance, Lanphear et al (2005) has associated maximal blood Lead levels lower than 7.5 μg/dL with permanent cognitive damage and intellectual deficits in children, whilst Menke et al (2006) associated 2 µg/dL as having increased risk of cardiovascular mortality in adults.

Foetuses, children, and pregnant women face the greatest risk (Schnaas et al, 2006; Iqbal et al, 2009).

References:

Borja-Aburto VH, Hertz-Picciotto I, Rojas Lopez M, Farias P, Rios C, & Blanco J (1999). Blood lead levels measured prospectively and risk of spontaneous abortion. American journal of epidemiology, 150 (6), 590-7 PMID: 10489998

Lustberg, M. (2002). Blood Lead Levels and Mortality Archives of Internal Medicine, 162 (21), 2443-2449 DOI: 10.1001/archinte.162.21.2443

Needleman HL, McFarland C, Ness RB, Fienberg SE, & Tobin MJ (2002). Bone lead levels in adjudicated delinquents. A case control study. Neurotoxicology and teratology, 24 (6), 711-7 PMID: 12460653

Canfield, R., Henderson, C., Cory-Slechta, D., Cox, C., Jusko, T., & Lanphear, B. (2003). Intellectual Impairment in Children with Blood Lead Concentrations below 10 μg per Deciliter New England Journal of Medicine, 348 (16), 1517-1526 DOI: 10.1056/NEJMoa022848

Needleman, H (2004). Lead poisoning Ann. Rev. Med (55), 209-222

Téllez-Rojo MM, Hernández-Avila M, Lamadrid-Figueroa H, Smith D, Hernández-Cadena L, Mercado A, Aro A, Schwartz J, & Hu H (2004). Impact of bone lead and bone resorption on plasma and whole blood lead levels during pregnancy. American journal of epidemiology, 160 (7), 668-78 PMID: 15383411

Lanphear BP, Hornung R, Khoury J, Yolton K, Baghurst P, Bellinger DC, Canfield RL, Dietrich KN, Bornschein R, Greene T, Rothenberg SJ, Needleman HL, Schnaas L, Wasserman G, Graziano J, & Roberts R (2005). Low-level environmental lead exposure and children's intellectual function: an international pooled analysis. Environmental health perspectives, 113 (7), 894-9 PMID: 16002379

Bellinger DC, & Bellinger AM (2006). Childhood lead poisoning: the torturous path from science to policy. The Journal of clinical investigation, 116 (4), 853-7 PMID: 16585952

Braun JM, Kahn RS, Froehlich T, Auinger P, & Lanphear BP (2006). Exposures to environmental toxicants and attention deficit hyperactivity disorder in U.S. children. Environmental health perspectives, 114 (12), 1904-9 PMID: 17185283

Ekong EB, Jaar BG, & Weaver VM (2006). Lead-related nephrotoxicity: a review of the epidemiologic evidence. Kidney international, 70 (12), 2074-84 PMID: 17063179

Menke, A. (2006). Blood Lead Below 0.48 mol/L (10 g/dL) and Mortality Among US Adults Circulation, 114 (13), 1388-1394 DOI: 10.1161/circulationaha.106.628321

Schnaas, L., Rothenberg, S., Flores, M., Martinez, S., Hernandez, C., Osorio, E., Velasco, S., & Perroni, E. (2005). Reduced Intellectual Development in Children with Prenatal Lead Exposure Environmental Health Perspectives, 114 (5), 791-797 DOI: 10.1289/ehp.8552

Schwartz, B., & Stewart, W. (2007). Lead and cognitive function in adults: A questions and answers approach to a review of the evidence for cause, treatment, and prevention International Review of Psychiatry, 19 (6), 671-692 DOI: 10.1080/09540260701797936

Cecil KM, Brubaker CJ, Adler CM, Dietrich KN, Altaye M, Egelhoff JC, Wessel S, Elangovan I, Hornung R, Jarvis K, & Lanphear BP (2008). Decreased brain volume in adults with childhood lead exposure. PLoS medicine, 5 (5) PMID: 18507499

Hauser, R., Sergeyev, O., Korrick, S., Lee, M., Revich, B., Gitin, E., Burns, J., & Williams, P. (2008). Association of Blood Lead Levels with Onset of Puberty in Russian Boys Environmental Health Perspectives, 116 (7), 976-980 DOI: 10.1289/ehp.10516

Jusko TA, Henderson CR, Lanphear BP, Cory-Slechta DA, Parsons PJ, & Canfield RL (2008). Blood lead concentrations Environmental health perspectives, 116 (2), 243-8 PMID: 18288325

Wright JP, Dietrich KN, Ris MD, Hornung RW, Wessel SD, Lanphear BP, Ho M, & Rae MN (2008). Association of prenatal and childhood blood lead concentrations with criminal arrests in early adulthood. PLoS medicine, 5 (5) PMID: 18507497

Iqbal S, Blumenthal W, Kennedy C, Yip FY, Pickard S, Flanders WD, Loringer K, Kruger K, Caldwell KL, & Jean Brown M (2009). Hunting with lead: association between blood lead levels and wild game consumption. Environmental research, 109 (8), 952-9 PMID: 19747676