SAS Urban Survival Handbook by John Wiseman Page A

muscles, and stunt mental development in children.
    Polycyclic aromatic hydrocarbons: From coal tar pitch, used to coat the inside of mains pipes (taken out of use in the UK in the mid-1970s). Suspected link with cancer.
    Industrial chemicals: Such as industrial degreasing agents and dry cleaning fluid. Suspected link with cancer. These are among the numerous chemicals pumped into streams and rivers when pollution controls are flouted.

LEAD
     
    Plumbing for water used to be made entirely of lead. In old houses this may still be the case. In updated systems, some lead piping may still be found as the connection to the water mains. Lead poisoning is extremely serious and in some cases debilitating or fatal. It attacks the brain and the nervous system. It affects the muscles. It causes anaemia. The effects can be devastating in young children.
    Some of the lead we absorb is from atmospheric pollution, but levels found in water samples indicate that water-borne lead is a major problem.
    The problem is worse in areas with soft water, because the pipes do not develop a protective coating of limescale (see Hard and soft water). Soft water may even dissolve small quantities of lead as it travels through the pipes. No lead plumbing should be considered safe, however.
    The long-term solution is to have ALL lead plumbing removed and replaced—but be prepared for a major upheaval.
    The short-term solution is to filter all drinking water (see Filtering water). Never drink water that has been standing in the pipes. Run the tap for a few minutes before drinking.
     
    Bacteria: Those of diseases spread by contact with human excreta are the most serious risk, though contamination is comparatively rare. In areas where bacterial diseases such as cholera are endemic, local water should be avoided in favour of a safer alternative even though you may be likely to be more at risk when you go swimming.
     
     
    Fluoride: Most supplies contain minute amounts. There is disagreement about the safety of adding sodium fluoride to water supplies in some countries/areas. This is done at a level of about one part per million, primarily to increase children’s resistance to dental decay—and is effective at doing so.
    Higher doses of fluoride during early tooth formation (possibly also because of fluoride dental treatments and fluoride supplements given to children) have been shown to produce a mottling of the teeth. This is common and only a cosmetic problem.
    Opinion as to whether there is any long-term health risk is divided—even scientific assessments have come up with conflicting results. In Britain, very few water authorities add fluoride to their supplies. There may be a health risk if you ingest quantities of fluoride from other sources as well (toothpaste, for instance). In higher doses (upwards of ten parts per million), fluoride is more widely believed to be a health hazard.

Filtering water
     
    Various filters are available. Some plumb directly into the drinking water pipe, others fit onto a tap. There are also two-part jug systems—tap water runs from a top section, through a filter, into a jug below. Most contaminants, including lead (but excluding nitrates), can be reduced or removed—but the replaceable filters work best when new. Decide for yourself whether the benefits outweigh the cost.

Hard and soft water
     
    Hard water basically contains more calcium and magnesium than soft water. The water filters described are good at removing ‘hardness’ when the filters are fairly new, yet there is evidence to suggest that hard water is better for you in some ways. Hard water dissolves less lead from pipes—it coats them with limescale. Evidence suggests that there are more cases of heart disease in areas with soft water. If this is true, the reasons have yet to be made clear.
    Hard water can damage plumbing systems by ‘furring’ up the inside of pipes and appliances. There are softeners which can be fitted to your system. The main