In a study focused more on pit latrines in developing countries than on Canadian outhouses, researchers at George Washington University School of Public Health and Health Services and the Department of Soil Science at North Carolina State University have published a review of what is known about the negative impacts of a popular sanitation method.
According to the article, an estimated 1.77 billion people use pit latrines as their primary means of sanitation. Groundwater contamination is frequently observed downstream of these latrines.
The researchers found only a limited number of studies that have explicitly examined links between groundwater pollution and contamination from pit latrines. Within these studies, the quality of experimental techniques and chosen indicator contaminants varied greatly. Nevertheless, based on available reports, researchers who looked for groundwater contamination from pit latrines frequently detected it, and studies observed travel distances of up to 25 m, 50 m, and 26 m for unsafe concentrations of bacteria, viruses, and chemicals, respectively. These contaminant transport distances could potentially be exceeded under certain conditions (e.g., in fractured rock aquifers), though most studies of pit latrine–derived contaminants actually showed transport distances that were less than half of the maximum values. Areas with shallow groundwater and areas prone to flooding present the greatest risks, because vertical separation is required between the base of latrine pits and the saturated zone.
Many Canadian parks have moved away from use of pit latrines and are now using toilets with holding tanks which are pumped out periodically. However, when sitting on the thunderbox in more remote parks and wilderness areas this holiday weekend, remember that you may be contributing to increased groundwater pollution.
The article is available currently in the online edition of the peer-reviewed Environmental Health Perspectives at http://ehp.niehs.nih.gov/1206028/