According to the Health and Safety Executive, asbestos is classed as a category 1 carcinogen (Source, HSE website: http://www.hse.gov.uk/asbestos/licensing/).
Cancer risks are clearly established and currently, 5000 people per year die from exposure to asbestos. 2,538 mesothelioma sufferers died in 2013. The estimated number of other lung cancers due to asbestos is likely to be around 2,000 and of asbestosis, 464 (2012 statisitics).
Blue and Grey asbestos (commonly regarded as the more dangerous materials) were banned from fresh installation in the UK in the mid 1980’s. White asbestos – mostly found in bonded products, so mixed with other stabilising materials such as cement, continued to be used until November 1999. At the time of writing (Aug 2014), in the USA asbestos was still being installed (.
Rather than being a new threat, the health risks of asbestos have been documented as far back as Ancient Greece when Pliny the Elder made reference to the ‘disease of the slaves’, after witnessing the respiratory problems of the workers who wove asbestos into cloth. He also recorded their use of rudimentary face masks which were designed to keep the fibres from being inhaled.
Today we know much more and the process of asbestos removal is tightly regulated. Three stage negative pressure air locks are employed, the workers wear breathing equipment, shower on leaving the work area and overalls are disposed of, not cleaned for re-use.
Bonded asbestos – sheeting, roofing and piping typically, is more secure. It doesn’t tend to release fibres unless disturbed – eg. snapped, drilled or when it becomes ‘friable’ as it ages. It is often handled by lay people and DIYers.
“There is no safe limit for asbestos exposure.” (Source, Cancer Research UK: http://scienceblog.cancerresearchuk.org/2014/01/20/the-link-between-working-with-asbestos-and-mesothelioma-case-closed/).
While those who work with asbestos over a period of time are higher risk of asbestosis, mesothelioma is as likely to be time sensitive. The latency for tumours is anything from 10 to 60 years after first exposure, with a mean figure of around 35 years.
Asbestos in the water table
Most concerns centre around the inhalation of asbestos fibres, but thought should also be given to fibres in the water table. Peritoneal mesothelioma (located in the abdomen) is not thought to come from ingested asbestos*, but there is no clear alternative cause. 35% of mesothelioma cases in Australia are peritoneal and 20% of those in the US. That does not include pleural (chest cavity) tumours which have spread.
Aside from the query over ingestion, fibres which are carried away in water may become airborne at another location when evaporation occurs.
* Update 26/8/15 (Source: http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Mesothelioma/Aboutmesothelioma/Causes.aspx)
On searching the NHS website for information on mesothelioma, you are directed to Macmillan Cancer Care who state:
“Asbestos fibres can also be swallowed, and some of the fibres can stick in the digestive system. They can then move into the outer lining of the abdomen (the peritoneum). Here, they cause swelling and thickening of the lining and can lead to peritoneal mesothelioma.”