Topic editor: Maria M. Williams
Lead author: Aleksandra Buha


On the night of January 30, 2000, a dam holding contaminated waters burst at a mining works in Bozinta Mare, Romania, and 100,000 cubic meters of cyanide-contaminated water (containing an estimated 100 tonnes of cyanide) spilled over some farmland and then into the SomeĊŸ River. The gold mining company, Aurul, was a joint venture of Australian company Esmeralda Exploration and the Romanian government.
The polluted waters eventually reached the Tisza and then the Danube, killing large quantities of fish in Hungary and Serbia. The spill has been called the worst environmental disaster in Europe since Chernobyl.

Causes of Baia Mare Environmental Disaster

The spill was the result of poor dam design and unusual weather conditions. The amount of precipitation during the winter of 1999 to 2000 was unusually high, which caused unexpectedly large amounts of water to accumulate in the pools. In addition to this, the days before the actual disaster were sunny and warm, resulting in snow and ice melting. These high amounts of water subsequently applied great pressure to the poorly built dam, and on the night of January 30, 2000, the dam experienced a fissure. The spill entered the Sasar River and made its way into the Somes River, which crosses into Hungary, then entered the Tisa River and the Danube. It entered Hungary on February 1 and Yugoslavia (Serbia) on February 12. It flowed into the Danube and so returned to Romania, finally entering the Black Sea.

Cyanide in the Environment

Cyanide is produced naturally in the environment by various bacteria, algae, fungi and numerous species of plants including beans, fruits, almond and cashew nuts, vegetables of the cabbage family, etc. Incomplete combustion during forest fires is believed to be a major environmental source of cyanide, and incomplete combustion of articles containing nylon also produces cyanide. Once released in the environment, the reactivity of cyanide provides numerous pathways for its degradation and attenuation.
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There is no reported biomagnification of cyanide in the food chain and therefore cyanide has a low chronic toxicity, although chronic cyanide intoxication exists.

Use of Cyanide in Gold Extraction

The use of cyanide allows the extraction of gold from sources that would otherwise be completely uneconomical since they contain only faint traces of gold. Specifically, cyanide bonds extremely well with gold and forms a soluble complex. Although this process is highly risky, mining companies that use the process argue that it is safe, and that the safeguards they set in place such as dams that hold back water are infallible. Therefore, mining companies are not prepared for the worst-case scenario and once disasters take place, companies cannot mitigate the effects properly.

Effects of Cyanide on Wildlife

Although cyanide reacts readily in the environment and degrades or forms complexes and salts of varying stabilities, it is toxic to many living organisms even at very low concentrations.

Aquatic Organisms: Fish and aquatic invertebrates are particularly sensitive to cyanide exposure and that sensitivity is highly species specific. Toxicity of cyanides is also affected by water, pH, temperature and oxygen content as well as the life stage and condition of the organism. Adverse effects include reduced swimming performance, inhibited reproduction, delayed mortality, pathology, susceptibility to predation, disrupted respiration, osmoregulatory disturbances, altered growth patterns, and the death of many species. Algae, macrophytes, and aquatic plants can tolerate much higher environmental concentrations of free cyanide than fish and invertebrates.

Birds: Symptoms including panting, eye blinking, salivation, and lethargy appear within one-half to five minutes after ingestion in more sensitive species, and up to ten minutes after ingestion by more resistant species. Exposures to high doses resulted in deep, labored breathing followed by gasping and shallow intermittent breathing in all species, whereas mortality typically occurred in 15 to 30 minutes.

Mammals: Symptoms of acute poisoning usually occur within ten minutes of ingestion, and include initial excitability with muscle tremors, salivation, lacrimation, defecation, urination, and labored breathing, followed by gasping and convulsions.

Consequences of the Baia Mare Disaster

More than 1,400 tons of fish have died as a result of this devastating environmental accident that destroyed the life basis for some hundred fishermen along the Tisza in Hungary. In some Rumanian and Hungarian towns the drinking water supply had to be shut down for some days. In Romania the village Bozinta Mare near the dam was most affected, with completely poisoned drinking water and soil.

The Aurul company, now Transgold, restarted the operation some months after the accident. Though Transgold has improved its safety standards, it is still under heavy criticism from environmentalists, especially because it continued to use cyanide. Transgold still has not paid compensation except for some compensation for the directly affected village of Bozinta Mare. As there have been no additional accidents in recent years, the river Tisza could slowly recover. Some fish survived the cyanide spill in river tributaries. Today the number of fish is close to the number before the accident, but there are still fewer species and commercial fishing is not possible. Read more