Thursday, 26 August 2010

Effect of climate change on human morbidity and mortality and sea levels
Climate change has been resulting in quite a many detrimental manifestations which tend to have a domino effect: fluctuations in temperature and precipitation (resulting in climate variability), as well as extreme manifestations such as drought, storms, rise in sea levels, and frequent severe weather events.

Consider the research by Grinsted et al (2009) who used a ‘physically plausible four parameter linear response equation’ to relate nearly 2,000 years of global temperatures and sea level. Assuming that this relationship holds from 200 to 2100 AD, IPCC’s temperature scenarios and reconstructed past sea level scenarios were used to visualise future sea level scenarios. The result suggests that climate change will lead to a 0.9-1.3 m change in sea level between 2090-2099. This bodes a certain flooding of low lying coastal regions and islands. Island countries such as Maldives would practically cease to exist. Whilst countries such as Bangladesh may not face such obliteration, such a sea level rise would flood 1/3rd of the country, displacing millions of humans and severely affecting agriculture, irrigation, and livestock.

Climate change also has a perceptible impact on human morbidity and mortality (Patz et al, 2005). Climate fluctuations have been linked to diseases and ailments- the evident effects of heat/cold (which, for instance, follows a U-shaped dose-response function with increased mortality in the extreme heat and cold), traumatic physical and mental ailments, and even cardiovascular and respiratory illnesses. This even results in altered transmission of infectious diseases (for instance, changes in temperature has been associated with salmonellosis in Europe and cholera in the ‘American south-west’; whilst, changes in rainfall has been associated with Rift valley fever in East Africa, and Hantavirus pulmonary syndrome and cholera in the American south-west and Bangladesh). When one factors in the effects of climate change on air pollution and the greater ecosystem, the result is quite chaotic. If the future projections of climate change are plausible, then it is likely that these health risks may rise significantly. The ‘potentially vulnerable’ regions includes the temperate latitudes (which may warm disproportionately), and the regions in and around the Pacific and Indian oceans (substantial rainfall variability).

But even though the economic North/developed countries are responsible for most of the greenhouse gas emissions, the damaging effects of their actions are most perceived in the poor countries of the South which has (as of yet) contributed least towards the GHG emissions.

Patz, J., Campbell-Lendrum, D., Holloway, T., & Foley, J. (2005). Impact of regional climate change on human health Nature, 438 (7066), 310-317 DOI: 10.1038/nature04188

Grinsted, A., Moore, J., & Jevrejeva, S. (2009). Reconstructing sea level from paleo and projected temperatures 200 to 2100 ad Climate Dynamics, 34 (4), 461-472 DOI: 10.1007/s00382-008-0507-2

Thursday, 19 August 2010

Where did the oil go? The recent oil spill in the Gulf of Mexico released, as we have all seen on tv, a lot of oil. Quite how much is a "lot" is a bit of a guess, but roughly 4.9 million barrels, or 784 million litres*. What actually happened to this oil was reviewed recently in an article in Science (Kerr 2010). Only about 0.1% was recovered from beaches and marshes (that´s still an awful lot of oil!). About 17% was siphoned away at the well head, 5% burned off at the surface, and only 3% skimmed off by booms, despite a lot of effort and money spent. And the other 75%? It's, er, disappeared.

So where did this oil go? Some evaporated, but with luck most of it was eaten.

Oil is energy, that's why we use it in our cars and power stations. And energy means food. There are actually quite a few bacteria that digest and breakdown crude oil, and these are massively important in the recovery of the ocean from disasters like this. They work as a consortium, each concentrating on a particular fraction of the oil, and as one hydrocarbon is degraded to another, other bacteria take over. The first, and so in many ways the most important, are Alcanivorax species (Vila et al 2010). These are found in tiny quantities in unpolluted waters, but their numbers rocket when in the presence of linear and branched alkanes, common in crude oil. In fact they are so specialised for this type of hydrocarbon that without long chain alkenes they grow very poorly, but by then their job is done. Now other species such as Roseovarius and Marinobacter take over.

This breakdown was helped by the massive release of chemical dispersants at the oil head, 1.1 million gallons (Kintisch 2010). These are similar to the detergent in your kitchen, breaking down lumps of oil into tiny droplets, which are "dispersed" and can be attacked much more efficiently by bacteria. This was very controversial, as dispersants are pretty toxic and an immense quantity was involved. Still, it seemed to work, and much of the oil was broken down into 1-10 micrometer droplets. In fact, it started to raise fears that it was working TOO well, a microbial explosion depriving the ocean floor of oxygen and creating a huge dead zone. But this seems not to have happened, and in fact so far the prognosis is good.

We´re not out of the woods yet, the oil could yet turn up in unwanted places, and chemical damage by detergents might yet, for instance, devastate the local tuna population. But there have been lessons learnt for next time - and there will be a next time.

Kerr RA (2010). Gulf Oil Spill. A lot of oil on the loose, not so much to be found. Science (New York, N.Y.), 329 (5993), 734-5 PMID: 20705818;329/5993/734?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=oil+biodegradation&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT

Kintisch E (2010). Gulf Oil Spill. An audacious decision in crisis gets cautious praise. Science (New York, N.Y.), 329 (5993), 735-6 PMID: 20705819

Vila, J., Nieto, J., Mertens, J., Springael, D., & Grifoll, M. (2010). Microbial community structure of a heavy fuel oil-degrading marine consortium: linking microbial dynamics with polycyclic aromatic hydrocarbon utilization FEMS Microbiology Ecology DOI: 10.1111/j.1574-6941.2010.00902.x

* the oil "barrel" is actually based on a type of old English wine barrel or "teirce" holding 35 gallons.

Wednesday, 4 August 2010

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.

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).


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


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