Itai-itai disease
, was the documented case of mass cadmium poisoning
Cadmium poisoning
Cadmium is an extremely toxic metal commonly found in industrial workplaces. Due to its low permissible exposure limit, overexposures may occur even in situations where trace quantities of cadmium are found. Cadmium is used extensively in electroplating, although the nature of the operation does...

 in Toyama Prefecture
Toyama Prefecture
is a prefecture of Japan located in the Hokuriku region on Honshū island. The capital is the city of Toyama.Toyama is the leading industrial prefecture on the Japan Sea coast, and has the industrial advantage of cheap electricity due to abundant water resources....

, Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, starting around 1912. The cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

 poisoning caused softening of the bones
Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism...

 and kidney failure. The disease is named for the severe pains (Japanese: 痛い itai) caused in the joints and spine. The term itai-itai disease was coined by locals. The cadmium was released into rivers by mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

 companies in the mountains. The mining companies were successfully sued for the damage. Itai-itai disease is known as one of the Four Big Pollution Diseases of Japan
Four Big Pollution Diseases of Japan
The were a group of manmade diseases all caused by environmental pollution due to improper handling of industrial wastes by Japanese corporations. Although some cases of these diseases occurred as early as 1912, most occurred in the 1950s, 1960s, and 1970s....



Itai-itai disease was caused by cadmium poisoning
Cadmium poisoning
Cadmium is an extremely toxic metal commonly found in industrial workplaces. Due to its low permissible exposure limit, overexposures may occur even in situations where trace quantities of cadmium are found. Cadmium is used extensively in electroplating, although the nature of the operation does...

 due to mining in Toyama Prefecture. The earliest records of mining for gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 in the area date back to 710. Regular mining for silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 started in 1589, and soon thereafter, mining for lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

, copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, and zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 began. Increased demand for raw materials during the Russo-Japanese War
Russo-Japanese War
The Russo-Japanese War was "the first great war of the 20th century." It grew out of rival imperial ambitions of the Russian Empire and Japanese Empire over Manchuria and Korea...

 and World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, as well as new mining technologies from Europe, increased the output of the mines, putting the Kamioka Mines in Toyama among the world's top mines. Production increased even more before World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Starting in 1910 and continuing through 1945, cadmium was released in significant quantities by mining operations, and the disease first appeared around 1912. Prior to World War II the mining, controlled by the Mitsui Mining and Smelting Co., Ltd., increased to satisfy the wartime demand. This subsequently increased the pollution of the Jinzū River
Jinzu River
The is a river that flows from Gifu Prefecture to Toyama Prefecture in Japan. It is called Miya River in Gifu. It is in length and has a watershed of .-Geography:...

 and its tributaries. The river was used mainly for irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

 of rice fields, but also for drinking water, washing, fishing, and other uses by downstream populations.

Due to the cadmium poisoning, the fish in the river started to die, and the rice irrigated with river water did not grow well. The cadmium and other heavy metals accumulated at the bottom of the river and in the water of the river. This water was then used to irrigate the rice fields. The rice absorbed heavy metals, especially the cadmium. The cadmium accumulated in the people eating contaminated rice.

The population complained to the Mitsui Mining and Smelting about the pollution. The company built a basin to store the mining waste water before leading it into the river. It was too little, too late as many people were already sick. The causes of the poisoning were not well understood and, up to 1946, it was thought to be simply a regional disease or a type of bacterial infection.

Medical tests started in the 1940s and 1950s, searching for the cause of the disease. Initially, it was expected to be lead poisoning due to the lead mining upstream. Only in 1955 did Dr. Hagino and his colleagues suspect cadmium as the cause of the disease. Toyama prefecture also started an investigation in 1961, determining that the Mitsui Mining and Smelting's Kamioka Mining Station caused the cadmium pollution and that the worst affected areas were 30 km downstream of the mine. In 1968 the Ministry of Health and Welfare issued a statement about the symptoms of itai-itai disease caused by the cadmium poisoning.

The reduction of the levels of cadmium in the water supply reduced the number of new disease victims; no new victim has been recorded since 1946. While the victims with the worst symptoms came from Toyama prefecture, the government found victims in five other prefectures.

The mines are still in operation and cadmium pollution levels remain high, although improved nutrition and medical care has reduced the occurrence of Itai-itai disease.


One of the main effects of cadmium poisoning is weak and brittle bones. Spinal and leg pain is common, and a waddling gait often develops due to bone deformities caused by the cadmium. The pain eventually becomes debilitating, with fractures becoming more common as the bone weakens. Other complications include coughing, anemia, and kidney failure, leading to death.

A marked prevalence in older, postmenopausal women has been observed. The cause of this phenomenon is not fully understood, and is currently under investigation. Current research has pointed to general malnourishment, as well as poor calcium metabolism relating to the women's age.

Recent animal studies have shown that cadmium poisoning alone is not enough to elicit all of the symptoms of Itai-itai disease. These studies are pointing to damage of the mitochondria of kidney cells by cadmium as a key factor of the disease.

Legal action

Twenty-nine plaintiffs, consisting of nine victims and 20 family members of victims, sued the Mitsui Mining and Smelting Co. in 1968 in the Toyama Prefectural court. In June 1971, the court found the Mitsui Mining and Smelting Co. guilty. Subsequently, the company appealed to the Nagoya District Court in Kanazawa, but the appeal was rejected in August 1972. The Mitsui Mining and Smelting Co. agreed to pay for the medical care of the victims; finance the monitoring of the water quality performed by the residents; and pay reparations to the victims of the disease.

People who consider themselves victims of itai-itai disease have to contact the Japanese Ministry of Health, Labor and Welfare to have their claims assessed. Many victims were not satisfied with government actions and demanded a change in the official procedures. This caused the government to review the criteria for recognizing a victim legally; the government also reassessed the treatment of the disease.

A person is considered to have itai-itai disease if he or she lived in the contaminated areas, has kidney dysfunctions, softening of the bones, but no related heart problems. One hundred eighty-four victims have been legally recognized since 1967, of whom 54 were recognized in the period from 1980 to 2000. An additional 388 people have been identified as potential victims, those that had not been officially examined yet. Fifteen victims were still alive .

Economic costs

The cadmium pollution had contaminated many agricultural areas. Heavy metal pollution affected many areas in Japan, and as a result the Prevention of Soil Contamination in Agricultural Land Law of 1970 was enacted. It ordered planting to be stopped so that restoration of the soil could be enacted to areas with 1ppm of cadmium or more contamination in the soil. Surveying in Toyama Prefecture began in 1971, and by 1977 1500 hectacres along the Jinzū river were designated for soil restoration. These farmers were compensated for lost crops as well as for lost production in past years by the Mitsui Mining and Smelting, Toyama Prefecture, and the national government. , only 400 hectares remained contaminated.

In 1992, the average annual health expense compensation was ¥743 million. Agricultural damage was compensated with ¥1.75 billion per year, or a total of annually ¥2.518 billion. Another ¥620 million were invested annually to reduce further pollution of the river.

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