How tap water gets polluted

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How do contaminants get in the water?

Water’s journey

If you live in a city, the water you drink takes a journey that looks something like this:

1. Meltwater from glaciers feeds streams and rivers. Many countries don’t have mountains and glaciers, hence why most residents of BC feel lucky about the quality of their water. However, as you will see below, there are many opportunities for the excellence of the water to be counteracted.

2. Streams and rivers feed reservoirs and water company treatment facilities. Water is the ideal transport mechanism – any pollutant that goes anywhere near water is likely to move through soil over time, and into the water table and rivers. This includes all the pesticides, insecticides, herbicides etc in agriculture, animal waste in farming, chemical pollutants from industry, acid and radioactive particles in rain, down to anything that someone throws down a domestic or storm drain. Amongst the most worrying of contaminants is the level of pharmaceutical and recreational drugs that end up in our water supply. We tend to ingest about 20% of any drug, and excrete the remainder. Water companies are not particularly attempting to remove these, as the levels are below levels considered dangerous. However, there is increasing coverage of the dangers of trace concentrations of Prozac, with the finger being pointed at links to autism, Cocaine (see here for Canada and here for general press coverage in the UK), and a number of other drugs (see here for a general article by Professor Joe Cummins, professor emeritus of genetics at the University of Western Ontario).

3. Water companies treat water that reaches them primarily for micro-organisms, with the aim of ensuring we don’t get immediately sick from the water. See above for more discussion on what the companies do and do not do to water.

4. After treatment, the water is sent via water mains to users. Water mains used to be made of rebar (iron-based), with concrete, and an asbestos liner. Over time, these mains corrode and crack, adding particles of iron, asbestos and other impurities into your water. This can be an indicator of past problems with your water supply, as corrosion means that the water was at times acidic, when pure water is neutral – although remember that the source of corrosion can be coming from outside the mains, in particular from untreated water seeping through the soil. Ageing water mains are a major issue in developed nations, as there is a huge infrastructure cost to replace them – which all water companies try to spread over as long a period as they can get away with. One way to almost literally “paper over” the cracks is artificially to raise the pH of water being transported. Whereas acid corrodes, and eats away at and other particles, alkalis deposit, meaning that they leave behind minerals which can coat the pipes – thereby prolonging their lives if they are beginning to crack. This is only a short-term solution, as over time the mains would get clogged up to an unacceptable level. You raise pH by adding chemicals (such as Sodium) to water. If mains are cracked, then pollutants from the soil will get into the water supply.

Two main possibilities exist for introducing contaminants into the treated water distributed through pipes: the pipes can crack, allowing more of the pollutants discussed above to get into the water, and the pipes themselves can corrode and leach chemicals into the water. There is a Canadian Guideline in Controlling Corrosion in Drinking Water Distribution Systems. This primarily interests itself in lead, given the proven health problems associated with lead ingestion. In section B.1.1, it states: “The principal contaminants of concern that can leach from materials in drinking water distribution systems are aluminum, antimony, arsenic, bismuth, cadmium, copper, iron, lead, nickel, organolead, organotin, selenium, tin, vinyl chloride and zinc. It is important to assess whether these contaminants will be present at concentrations that exceed those considered safe for human consumption.” Remember from the discussion above that what is currently considered safe for human consumption is unlikely to be considered safe in the near future. Also these are just guidelines, which of course can be breached. Check here for news in May 2014 of serious levels of lead contamination in Toronto homes – where it is reported that 13% of Toronto homes have unsafe levels of lead, and that this is when measured against a level of safety that is outdated according to recent research:

“The (10 parts per billion threshold) is obsolete,” says Dr. Bruce Lanphear, a health sciences professor who specializes in lead exposure in children at Simon Fraser University. “We’ve got science that is conclusive, definitive and evaluated by independent advisory boards but policy hasn’t kept up with that.”

Lanphear said Toronto’s 13-per-cent failure rate is a serious concern. “That’s excessive and unacceptable from a public health perspective.” ”

Also it’s slightly surprising that the list of contaminants of concern does not include asbestos, which is a by-product of  corrosion in Asbestos-Cement (A/C) pipes. A World Health Authority report on asbestos in water published in 2003 cited that A/C pipes are used in 19% of Canadian homes. It went on to state, however, that there is no proven link to cancer from drinking water, while there is for airborne asbestos – hence possibly why asbestos is not seen as a concern. However, since then there have been studies showing exactly that link to asbestos in drinking water. The Canadian Cancer Society is pretty clear about the link to cancer.

5. Water is distributed from water mains to water pipes on your property. The same risks of contamination exist with your pipes as with water mains, the only difference being that it’s YOU that’s responsible for these pipes. Once the water arrives at your property, it is your pipes that transfer it from the mains to your faucets. The same processes as described for the mains apply to your pipes, with older pipes ending up clogged or corroded, and either transferring particles from themselves (old lead pipes are particularly dangerous in this regard) or allowing contaminants to come through cracks into your water.

6. Finally the water comes through the pipes to your faucet. Again there can be corrosion through the faucet.

If you are living over well water, then you are likely already accepting that your water is polluted. All the natural and artificial impurities from miles around end up in the water table by a process of natural leaching.