Mercury exposure affecting workers

Project Duration:
April, 2006 – July 2007
Project Cost:
Implementation Partners:
Redlog Environmental Ltd., Dr. Tom Murphy – lead technical advisor
Ratankirri, Cambodia
Southeast Asia,
Mining, Mercury, Artisanal Mining


Project Completion Report (PDF)

Cambodia is amongst the poorer countries in the world, ranking 130 or 177 countries in the 2003 Human Development Index, as reported by the UN.  The GNI per capita in 2004 was $320, while life expectancy was 57 years.  Mortality due to waterborne illnesses is high, in part reflecting the fact that many Cambodians have less access to adequate sanitation and clean drinking water compared to other Asian nations.  The country is still struggling to recover from recent civil war (1970-5), and Khmer Rouge tragedy (1075-9) and subsequent occupation by Vietnam (1979-89).  A generation of technically-skilled people was killed or fled the country and all government institutions were mantled.  As such, there is a great need to capacity building in the areas of natural resource, environment, and basic health management. 

The province of Ratanakirri is an isolated underdeveloped area of northeast Cambodia with a small population of about 72,000.  About 80% of the people are tribal who subsist by slash and burn agriculture and fishing.  Gold and gem stones are fathered in crude mines at times using mercury to extract gold.  A review by Sotham (2004)  estimated that about 1000 miners are working at six Prey Meas mines.  They use mercury amalgamation, without retorts, to extract the gold.  The concentration of mercury in the hair of the miners was extremely high; in April 2006 retorts were successfully introduced into a goldmine in Prey Meas to recover mercury.  The technology was readily understood, and the miners were glad to be both protecting their health and recouping some of their expense.  This initial project was quite small and more effort should be directed at introduction of retorts at more mines.  Any effort to introduce retorts at more mines should be associated with an attempt to measure the total amount of mercury escaping from the mines.  The objective of this project is to reduce the negative, mercury-related, community health impacts of artisanal gold mining operations.


The study team looked at two gold mines in Ratanakirri province that are very isolated and the communities suffer greatly from a lack of clean water and basic education.  Mercury analysis from samples taken (from human hair, fish, soil, mine tailings) were performed at Environment Canada’s laboratories in Burlington, Ontario.  The tailings were analyzed for acid volatile sulfide (AVS) and the pH of local waterways was measured. 

The hair samples demonstrated a level of mercury high enough to be associated with fertility problems; some individuals had levels high enough to result in peripheral vision loss, stunted child development, and nervous system dysfunction.  Workers in the mine showed a slightly lower than local average level of mercury, but this could be due to amount of time spent working at the mine, and specific duties performed.  

Successful introduction of simple retorts and effective environmental and health management must include both increased capacity and education.  


Simple pit latrines and ceramic filters were provided to the families at the two study mines, and were accompanied by an education program focusing on proper sanitation and clean drinking water practices.  Health surveys were performed before and after these introductions.  

After retorts made locally in Cambodia were introduced, craftsmen were trained to create and utilize them. Mercury was effectively trapped in the retorts.  It was found that miners preferred a glass-topped retort.   

Blacksmith also measured severe bacterial contamination in the community drinking water well and provided a ceramic water filter that removes all bacteria.

Follow Up

Continuing education and an increased number of retorts are the primary follow-up activities recommended by Blacksmith.