Arsenic/Lead in Drinking Water Flashcards
Lead in Drinking Water Pipes in Canada
- Commonly used in drinking water systems because it is easy to shape and resistant to corrosion compared to Fe
- National Plumbing Code of Canada allowed Pb as an acceptable material in pipes until 1975 and in solder until 1986
Lead in Drinking Water in Calgary
- Our drinking water quality meets or performs better than all federal and provincial health guidelines
- Pb is not found in Bow or Elbow Rivers
- Pb service pipes: were installed in Calgary from 1939-1947, and most have been replaced (~593 houses left with Pb service pipes)
- Pb solder in household pipes: houses built prior to 1989 may have Pb solder. Corrosion or breakdown could cause Pb to leach into the water. Licensed plumber can determine if a home contains lead solder, lead pipes or pipe fittings
Lead cannot be seen, smelled, or tasted in water. The only means to measure Pb lvls in a home is testing water collected at the tap.
- Residents can arrange for Pb testing by a private lab
- All pipes on private property are the responsibility of the property owner
Arsenic is known throughout history as a classic poison
- <1g can cause death in a matter of hours
- Ancient and medieval times: favoured by assassins
- Relatively easy to obtain
- Lacks odour or taste when mixed in food or drink
- Overdose causes abdominal cramping and vomiting -> hard to distinguish from unintentional food poisoning
Average crustal abundance of As:
1.5mg/kg = 1.5ppm
Current WHO guidelines for As in drinking water
Max As = 10ug/L = 10ppb (USA and Canada’s guidelines too)
Uses, Mining and Production
- Component of insecticides, weedkillers, and wood preservatives
- Used in pigments for wallpapers, paints, ceramics
- A component in electronics, semiconductors
- Occurs in association with minerals containing Cu, Ni, Co, Pb, Ag, Sn, and has been produced as a byproduct of mining these metals
- [As] in soil and rocks near mining/smelting activities are 100-1000x higher than avg
As in shallow groundwater in Southern Asia
What happened (and is happening): rural pops in West Bengal and Bangladesh changed their water supply from rivers/streams to groundwater (wells)
Reason: To avoid pathogens
Consequences: much higher lvls of As in groundwater, unexpected
Started digging these wells in the 1940s, most were dug in the 1970s. In the early ’80s, it became clear that ppl in SE Asia were affected by prolonged exposure to high As lvls
- Skin lesions, skin - bladder - kidney - lung cancers, heart disease
- 20mil ppl exposed in Bangladesh, 300k currently have skin lesions and cancers
How is Drinkwell helping the ppl of rural Bangladesh?
Built 30 water treatment facilities, remove As and bacteria, does not need electricity to run. Many more need to be built
As of April 2016, the Bangladesh govt is failing to adequately respond to naturally occurring As in drinking water across large areas of rural Bangladesh.
Approx 20yrs after initially coming to international attention, an est 20mil ppl in Bangladesh - mostly rural poor - still drink water contaminated over the national standard
Why so much As in these groundwaters?
- Not from mining. Scientific consensus is that As occurs naturally in the host rocks of aquifers
- Exact mineral host for As is still a matter of intense debate
Why is As being mobilized?
Ideas:
1) Oxidation of As-rich minerals from drawdown of water at well sites
2) Input of phosphate from irrigated fields + competitive adsorption
3) Microbial dissolution of As-rich minerals
Why can’t Kettleman City use water from the California aqueduct?
Need a water treatment plant, but delay after delay in building one
What is the source of the As in Kettleman City’s drinking water?
Unknown
