A report on liquefaction silt prepared after the September 2010 Christchurch earthquake rated as low the health risk from dust generated from earthquake liquefaction and sewage contamination.
A report on Liquefaction Silt - Public Health Risk prepared after the September 2010 Christchurch earthquake rated as low the health risk from dust generated from earthquake liquefaction and sewage contamination.
The Institute of Environmental Science and Research report, based on international experience and some limited local testing, finds the dust is largely a nuisance, which due to its small particle size can be inhaled into the lungs and exacerbate respiratory conditions such as asthma. However, the scientists caution that the report was a small-scale study performed some weeks after the September earthquake, on only a few samples of dry silt from a single location so may not necessarily apply to the silts in Christchurch now.
However, following the February 2011 Christchurch earthquake, in parts of the city sewerage pipes were broken or damaged. People should avoid sewage and silt that may have been contaminated with sewage, even if it is on their properties. If people have to work with silt they should wear water-proof gloves, gumboots and a dust mask. People should also shower or wash thoroughly immediately after contact with either sewage or silt, and wash clothes separately.
Christchurch public health staff advise that earthquake generated silt and dust should be treated as potentially contaminated and the usual precautions should apply when dealing with it. Anyone coming into contact with the dust should wash and dry their hands, use hand sanitiser and wear a mask if susceptible to dust.
Any Christchurch residents concerned about the level of dust and other pollutants in the air should wear an appropriate dust mask to protect your lungs.
These masks are usually available from hardware stores and pharmacies.
ESR Ltd undertook research work following the earthquakes in Christchurch to support public health advice in a similar situation. The studies report on the effects of the Christchurch earthquakes on ground water, dust and silt. The reports are:
- Sewage-Contaminated Liquefaction Silt Study
- PM10 and Christchurch Liquefaction Silt
- Microbial Quality of the Avon River: The effect of major earthquakes and subsequent sewage discharges on the quality of the water and sediments in the Avon River
- Summary of Literature Impacts of Earthquakes on Groundwater Quality.