A study on exposure to cyanide among a community living near a gold mine in Malaysia.

Author:Hassan, Noor Artika
Position:INTERNATIONAL PERSPECTIVES - Report
 
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Introduction

Malaysia is well endowed with natural mineral resources. One of the minerals that captivates people is gold. Gold mining in Malaysia began in the 18th century (Metcalfe, 1990). Gold production in this Southeast Asian country increased substantially from 2,489 kg in 2008 to 2,794 kg in 2009 from five gold mines in Pahang, Kelantan, and Johor (Tse, 2010).

Shaft mining was previously used to extract gold (Metcalfe, 1990). During ancient times, large pieces of gold could be extracted with relatively primitive methods and tools, with minimal disturbance to the environment (Muezzinog'lu, 2003). Today, however, cyanidation methods, also known as carbon in leach, have been used extensively in gold extraction, and these methods have a detrimental impact on the ecosystem. The cyanidation method is a simple, straightforward, and popular method for low-grade gold ore processing. Very dilute solutions of sodium cyanide (NaCN) are used in gold mining operations, typically in the range of 0.01% to 0.05% cyanide (100 to 500 parts per million [ppm]) for the process of leaching (Logsdon, Hagelstein, & Mudder, 1999). A stable gold-cyanide complex is then formed once the cyanide dissolves the gold from the ore (International Cyanide Management Code [ICMC], 2010).

Despite its popularity, the sodium cyanide method or cyanidation is highly controversial due to its toxicity. It can cause adverse effects on the ecosystem and the population living around the mining area (Moran, 2004). Although free cyanide breaks down rapidly when exposed to sunlight, the less toxic products, such as cyanates and thiocyanates, may persist in the environment for many years. Due to its toxic impact, cyanidation has been banned in the Czech Republic and in the state of Montana, while Turkey and Greece have been discouraging its use and other U.S. states are considering restricting its use (Haiduc, 2005; Muezzinog'lu, 2003; O'Reilly, Dicinoski, Miura, & Haddad, 2003).

Exposure to cyanide causes several side effects. The effects of acute cyanide exposure are dominated by central nervous system and cardiovascular disturbances (Agency for Toxic Substances and Disease Registry [ATSDR], 2011). Typical signs of acute cyanide poisoning include tachypnea, headaches, vertigo, lack of motor coordination, weak pulse, cardiac arrhythmias, vomiting, stupor, convulsions, and coma (Ballantyne, 1983; Johnson & Mellors, 1988; Way, 1984). Pathological findings may include tracheal congestion with hemorrhage, cerebral and pulmonary edema, gastric erosions, and petechiae of the brain meninges and pericardium (Way, 1984).

The effects of chronic cyanide exposure are confusion, hallucination, hypo--or hyperthyroidism, abdominal pain, thyroid enlargement, and slurred speech. Baskin and coauthors (2009) stated that chronic cyanide exposure may lead to a kinetic rigid syndrome, tremors, pathological reflexes, disorders of sensitivity, intellectual deficits, and significant neurological morbidity arising from the apoptotic demise of neurons of the basal ganglia and sensory-motor cortex. El Ghawabi and co-authors (1975) found that hemoglobin and lymphocyte counts were higher among exposed workers.

In Malaysia, limited published research exists on the health impacts of cyanidation on communities near gold mining operations. Therefore, our study was conducted in a community living near a gold mine to assess the effects of low-dose exposure to cyanide via gold mining through residents' urinary thiocyanate levels and self-reported symptoms. The level of urinary thiocyanate can be influenced by the distance from the gold mine and can also be affected by other factors such as smoking (Hernan, Olek, & Ascherio, 2001; Scherer, 2006) and food (ATSDR, 2006; Logsdon et al., 1999).

Our study had three major aims: 1) to compare the urinary thiocyanate levels of the exposed and the control communities; 2) to compare the prevalence of cyanide exposure symptoms of the exposed and the control communities; and 3) to provide additional information on lifestyle factors that have been associated with urinary thiocyanate levels such as demographic factors, dietary exposure, and smoking.

Methods

Our cross-sectional study was conducted on the east coast of Peninsular Malaysia. The study area was selected to address community concerns about the impact of gold mining activities on residents' health. It covered 372 adults, aged 18 to 70 years old, who were randomly recruited from two communities. The first community was within a 5 km radius from a gold mine; it included 255 respondents and was classified as the exposed community. The control community was comprised of 117 respondents who were living farther away. The location of the control community was 13.6 km from a gold mine, which was more than 5 km beyond the buffer zone. The members of both communities have similar ethnicities, including Malay, Chinese, and Indian. Both locations are rural areas.

The study protocol was reviewed and approved prior to its implementation by the ethics committee of the Universiti Kebangsaan Malaysia Medical Center. The respondents gave their written consent before participating in our study.

Survey

A survey was conducted among the communities in February 2011 using a modified and validated guided questionnaire (Veiga 6 Baker, 2004). The questionnaire was translated into Malay and obtained information on demographic characteristics, medical history, cigarette consumption, working exposure, food and water sources, and self-reported symptoms that could be associated with mining activities. Respondents were asked about their sources of water, vegetables, fruits, beef, chicken, duck, and pork to investigate the possibility of cyanide being transmitted through dietary intake. In addition, an open-ended questionnaire was used to obtain information on the intake of food such as almonds, millet sprouts, lima beans, soy, spinach, bamboo shoots, and cassava roots, as these foods contain a relatively low amount of cyanide. Those who had consumed foods that may contain...

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