Itai-itai disease is caused by the toxicity of:

Itai-itai disease is a painful disease caused by chronic cadmium poisoning. It was first identified in the Toyama Prefecture of Japan around 1912 and became widespread in the 1950s. The name means "it hurts-it hurts" in Japanese ("itai" means "ouch" or "painful"), because of the severe pain in the bones and joints that patients suffered.

The disease was caused by mining companies in the mountains upstream, especially the Kamioka mine, which released cadmium-contaminated waste into the Jinzu River. Farmers used the river water to irrigate rice fields, and cadmium accumulated in the rice. People who ate this rice and drank the contaminated water over many years absorbed cadmium into their bodies.

Cadmium accumulates mainly in the kidneys and damages them. This disturbs the body's handling of calcium and phosphate, causing the bones to become soft, weak and brittle (osteomalacia and osteoporosis). Patients suffered from fractures, often from minor stress, severe pain, and kidney failure. Women, especially those who had given birth to many children, were most affected. It was one of the "Four Big Pollution Diseases" of Japan, which led to stronger environmental laws there.

Cadmium is a heavy metal used in nickel-cadmium (Ni-Cd) batteries, pigments, electroplating, plastics and solar panels. It is also present in cigarette smoke and phosphate fertilisers. Heavy metals are dangerous because they do not break down and can accumulate in living organisms (bioaccumulation) and increase along food chains (biomagnification).

Diseases caused by other heavy metals:

Minamata disease: mercury poisoning (from eating contaminated fish), first identified at Minamata Bay, Japan, in 1956. The Minamata Convention on Mercury was adopted in 2013.

Plumbism (lead poisoning): affects the brain and nervous system, especially in children.

Arsenicosis (arsenic poisoning): causes skin lesions and cancer, a serious problem in groundwater in West Bengal and Bangladesh.

Blue baby syndrome: caused by excess nitrates in drinking water.

Black foot disease: caused by arsenic, reported in Taiwan.

Why not the other options?

• ✗Mercury causes Minamata disease.
• ✗Lead causes plumbism.
• ✗Arsenic causes arsenicosis and black foot disease.