In conclusion, heavy metals are an important part of our environment and a growing threat to our health. As I have explored over the course of my blog, heavy metals, such as mercury, have been influencing us since we first began to evolve and pose a significant threat to our well being when their emissions are not monitored. Consumption is the most common route of poisoning. As seen with Minimata and the USA, mercury is primarily ingested through fish and other sea food. It is successfully transferred up the tropic levels and thus reaches toxic levels at higher tropic levels. Similarly cadmium, passes into the food chain through plants and crops, which have a higher tolerance for the metal than animals or humans. Arsenic has similar properties to cadmium, it readily moves through the soil or rock and displays a high tolerance in vegetation yet when ingested by humans can have severe health implications, as seen in the case of Bangladesh, where the main source of poisoning was water resources in the Ganges.
One cannot ignore the importance of industry in the global contamination of heavy metals. Industry as far back as the classical era, during the Greeks and Romans, is responsible for high levels of heavy metal emissions. The main source of poisoning at Minimata was industrial actions and many marine polluted areas are near industrial outputs. Understanding their harmful effects and past emissions is crucial to being able to understand the current threat and how to mitigate potential harmful effects in the future. In many cases, the lesson at Minimata and in other parts of the world, has still not been learnt or is ignored for economic gain. Evidence found in ice cores shows that heavy metal pollution is not a new phenomena and has the potential to topple entire empires and as such it should be taken seriously.
Writing this blog has been an interesting experience where I have been able to explore a wide range of material and research. The topic chosen was broad and looked at a very interesting aspect of environmental pollution that is not always fully portrayed in modern forms of media, unlike climate change or deforestation. I believe it has been a valuable experience that has allowed me to develop key skills in both analytical and research fields. I would have enjoyed to have explored the other metals considered toxic and have gone into more depth about the modern roles of copper and lead.
I hope you enjoyed Highway to Bad Hell-th: Heavy Metal Pollution.
Tuesday, 3 May 2011
Monday, 2 May 2011
Ancient Civilisation Contributions to Heavy Metal Pollution
Almost everywhere we look we are told that our activities are harming our environment. We are lead to believe that climate change and pollution are relatively recent phenomena started by the industrial revolution but there is a lot of evidence to suggest that we have been shaping and polluting out surroundings for far longer than the last one hundred years or so.
The Greeks and Romans were some of the most prolific civilisations in ancient history and have been revered and studied for hundreds of years. Our understanding of literature and archaeological evidence shows they had a very sophisticated use for many heavy metals still in heavy industry and use today, the most common of which is lead (Pb) and Copper (Cu). As discussed in my previous post, there is significant evidence in Greenland ice cores showing that these metals have been highly variable in the atmosphere for many millennia and have significant natural sources. Yet peaks could be observed at certain points throughout the last few thousand years, most notable, during the existence of early civilisations.
Hong et al. (1994) wrote a research paper detailing the Greenland ice evidence supporting lead pollution specifically by the Greeks and Romans. They estimate that anthropogenic lead pollution started almost 6 millennia ago and primarily came from the smelting of lead-silver alloys. The ice core results they found suggested that during the Roman era the emissions reached 800,000 metric tonnes per year, similar to those found during the industrial revolution. This lead was sourced from Spain, the Balkans, Greece and Asia. Most smelting was done in Spain in open air furnaces with no emissions controls.
Yet this was not sustained, it declined to only a few hundred metric tons per year during the medieval era, it only increased following the discovery of new mines in central Europe. Perhaps the most astounding claim that Hong and his colleagues make is that lead was an integral part to the fall of the Roman Empire. It was suggested that mass poisoning was due to mass regional deposits of lead and further evidence can be gained from peat bogs in Britain. The high level usage of lead in smelting the Romans is also responsible for one of the largest hemispheric pollutions on record, with large deposits of lead making it into the troposphere and to remote areas of the Arctic.
A follow up paper can be found in a later issue of 'Science', also written by Hong, in 1996. This article outlined the pollution of copper (Cu) because of it's use in Roman and Medieval times from the analysis of another Greenland ice core. Hong states that copper pollution and emissions was actually higher before the industrial revolution that in was afterwards. This is mainly due to the techniques employed during the pre-industrial copper industries, smelting and mining practices were far less cleaner and less efficient.
Copper was first produced around 7000 years ago and production reached it's peak around 5000 years ago after smelting was developed and demand for tin bronze rose during the Bronze Age. The technique of smelting was modified with the introduction of sulphide around 45000 years ago causing production to increase again. From the ice core, Hong estimates that between 4000 and 2700 years ago, half a million metric tonnes of copper was produced. The demand for coinage during the Roman era 2000 years ago meant a record high of 15,000 metric tons was produced in one year. Hong also commented that between 2250 and 1650 years ago Spain and Cyprus were the main producers and exporters of copper, resulting in 5 million metric tons being created between them during this time period.
The smelting of copper didn't just mean that copper pollution became a problem in the classical era. When smelting copper for weapons, high levels of arsenic were used in the process that was then disposed of irresponsibly. This meant that many ground water reservoirs in areas producing copper reported high levels of arsenic and thus arsenic poisoning of water resources. Copper production finally declined with the fall of the Roman empire, it was picked back up again in Medieval times but the production was not on the same scale as those found in the ice core during Roman times.
Both of Hong's papers are highly informative and give a comprehensive overview of the production of heavy metals in Roman, Greek and Medieval times. The paper's show the scale of production and plenty of numerical evidence for the scale of pollution during these times in comparison to more recent industry. They are another contribution to the argument that heavy metals are indeed an important aspect we should be considering in environmental pollution. Having said that, I feel the methodology and science behind the examples and figures was not fully explained and I would have liked to have read more about it.
The Greeks and Romans were some of the most prolific civilisations in ancient history and have been revered and studied for hundreds of years. Our understanding of literature and archaeological evidence shows they had a very sophisticated use for many heavy metals still in heavy industry and use today, the most common of which is lead (Pb) and Copper (Cu). As discussed in my previous post, there is significant evidence in Greenland ice cores showing that these metals have been highly variable in the atmosphere for many millennia and have significant natural sources. Yet peaks could be observed at certain points throughout the last few thousand years, most notable, during the existence of early civilisations.
Hong et al. (1994) wrote a research paper detailing the Greenland ice evidence supporting lead pollution specifically by the Greeks and Romans. They estimate that anthropogenic lead pollution started almost 6 millennia ago and primarily came from the smelting of lead-silver alloys. The ice core results they found suggested that during the Roman era the emissions reached 800,000 metric tonnes per year, similar to those found during the industrial revolution. This lead was sourced from Spain, the Balkans, Greece and Asia. Most smelting was done in Spain in open air furnaces with no emissions controls.
Yet this was not sustained, it declined to only a few hundred metric tons per year during the medieval era, it only increased following the discovery of new mines in central Europe. Perhaps the most astounding claim that Hong and his colleagues make is that lead was an integral part to the fall of the Roman Empire. It was suggested that mass poisoning was due to mass regional deposits of lead and further evidence can be gained from peat bogs in Britain. The high level usage of lead in smelting the Romans is also responsible for one of the largest hemispheric pollutions on record, with large deposits of lead making it into the troposphere and to remote areas of the Arctic.
A follow up paper can be found in a later issue of 'Science', also written by Hong, in 1996. This article outlined the pollution of copper (Cu) because of it's use in Roman and Medieval times from the analysis of another Greenland ice core. Hong states that copper pollution and emissions was actually higher before the industrial revolution that in was afterwards. This is mainly due to the techniques employed during the pre-industrial copper industries, smelting and mining practices were far less cleaner and less efficient.
Copper was first produced around 7000 years ago and production reached it's peak around 5000 years ago after smelting was developed and demand for tin bronze rose during the Bronze Age. The technique of smelting was modified with the introduction of sulphide around 45000 years ago causing production to increase again. From the ice core, Hong estimates that between 4000 and 2700 years ago, half a million metric tonnes of copper was produced. The demand for coinage during the Roman era 2000 years ago meant a record high of 15,000 metric tons was produced in one year. Hong also commented that between 2250 and 1650 years ago Spain and Cyprus were the main producers and exporters of copper, resulting in 5 million metric tons being created between them during this time period.
The smelting of copper didn't just mean that copper pollution became a problem in the classical era. When smelting copper for weapons, high levels of arsenic were used in the process that was then disposed of irresponsibly. This meant that many ground water reservoirs in areas producing copper reported high levels of arsenic and thus arsenic poisoning of water resources. Copper production finally declined with the fall of the Roman empire, it was picked back up again in Medieval times but the production was not on the same scale as those found in the ice core during Roman times.
Both of Hong's papers are highly informative and give a comprehensive overview of the production of heavy metals in Roman, Greek and Medieval times. The paper's show the scale of production and plenty of numerical evidence for the scale of pollution during these times in comparison to more recent industry. They are another contribution to the argument that heavy metals are indeed an important aspect we should be considering in environmental pollution. Having said that, I feel the methodology and science behind the examples and figures was not fully explained and I would have liked to have read more about it.
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