Chemicals and toxins

Continued economic growth and industrial activity has contaminated much of the world’s fresh water supply with manufactured chemicals.

The range of contaminants includes toxic heavy metals, such as lead, mercury and cadmium, agricultural chemicals such as pesticides and fertilizers (nitrates) and volatile organic chemicals such as gasoline / petrol and solvents.

Sources of contaminants include agricultural and golf course run-off, industrial run-off from pulp mills, chemical plants, manufacturing plants, run-off from roads, acid rain from airborne pollution and leaching from landfill sites, mines and septic fields.

Generally, the more people who live in an area the greater the level of chemical pollution. Many recreational areas, and some wilderness areas, are downstream or downwind from industrial zones or agricultural areas, which ensures continuous contamination.

For example, 39% of all groundwater wells in South Dakota have levels of nitrate that exceed US national drinking water standards. The nitrate is from fertilizer contamination of aquifers and is in high enough concentrations to harm children. Across eastern Canada, the US and eastern Europe, acid rain has rendered thousands of lakes essentially lifeless. Ice core samples from the Canadian arctic and Antarctica confirm that chemicals are transported all over the world by weather systems.

Some chemicals that are now banned in North America and Europe, such as DDT, are sometimes still manufactured and used in developing countries. Even after a chemical is banned it can often persist for years, decades or potentially indefinitely in the environment of any country. Furthermore, mining or mill slag heaps, abandoned industrial areas, lake and river sludge adjacent to industrial areas and other sources will remain sources of chemical leaching into groundwater, rivers and lakes far into the future causing local and trsnboundary problems.

A Few Words on Risks

Given the proliferation of chemicals in the environment and the scale of the problem, the purpose of this section is to outline the chemicals and elements that may be present in water in recreational and wilderness areas and to assess the potential dangers of drinking such water.

It must be noted that very few chemical and elemental contaminants are found in water in recreational and wilderness areas in sufficient concentrations to cause immediate illness or death. Many of the effects are longer term and relate to organ damage and cancer.

However, the most difficult task in assessing the non-microbiological risk of drinking is determining what harmful chemicals or elements might be in the water without sending a sample to a lab.

How exactly do you assess the quality of water when you are out adventuring? The short answer is that you can’t. However you can do some research before heading out to help you predict with reasonable certainty what contaminants you might encounter and how to deal with them. The section of the website on treatment systems offers some advice on these points.

The Special Case of Nitrate

The one chemical that is often present in water at high enough levels to cause immediate harm is nitrate, which gets into the environment through chemical fertilizers, animal wastes and septic systems.

Nitrate poses a greater risk for recreational travellers than any other chemical because of widespread agriculture and livestock ranching, and the potentially deadly affect on babies.

In the digestive system of an infant, a certain type of bacteria converts nitrate into nitrite. Nitrite reacts with hemoglobin, which carries oxygen in the blood, to form methemoglobin, which cannot carry oxygen. The end result is oxygen depletion in the baby.

This illness is called methemoglobinemia, or ‘blue-baby’ disease or syndrome, and is characterized by symptoms of suffocation including bluish skin, particularly around the eyes and mouth.

The infant must be immediately hospitalized for treatment to convert the methemoglobin back into hemoglobin.

After infants reach six months of age, their stomachs usually no longer harbour large numbers of the bacteria that convert nitrate into nitrite because of an increased level of hydrochloric acid. Infants under this age should not be exposed to any water sources that have even a remote possibility of nitrate contamination, especially water from agricultural and ranching areas, golf courses or near septic fields.

Elements, Chemicals and Heavy Metal Contaminants

The following chart, derived from Health Canada and US EPA guidelines, summarizes the major chemical and elemental contaminants that have been detected in North American water supplies. Both Health Canada and the US EPA use specific terms to quantify the levels of chemical contaminants in drinking water. European systems are broadly similar if perhaps tighter following recent EU regulations on chemicals.

Health Canada’s levels are based upon an average daily intake of one and a half litres of water by a 70 kilogram adult and a large safety factor of up to ten is considered when determining the levels. Important definitions for the chart are: Health Canada’s Maximum Acceptable Concentration (MAC), which is the maximum level of concentration permitted for ‘substances that are known or suspected to cause adverse effects on health.’

The US EPA’s equivalent term, Maximum Contaminant Level (MCL), which ‘is the highest amount of a specific contaminant allowed in the water delivered to any customer of a public water system.’

When possible the Health Canada MAC or US EPA MCL is provided. Most importantly, a brief description of the possible sources of contamination and possible health effects is given. This should help you to assess the quality of water sources based on geographic location and make judgement calls about the risks of drinking water that may contain possible contaminants.