Which metal is mainly responsible for causing the painful Itai-Itai disease in humans as a result of environmental pollution and contaminated water or rice?

Introduction / Context:
Itai Itai disease is one of the classic examples of a pollution related health disaster described in environmental chemistry and public health studies. The disease name comes from the severe pain suffered by affected people. This question asks which specific metal is responsible for Itai Itai disease, highlighting the importance of understanding heavy metal toxicity and its impact on human health.

Given Data / Assumptions:

• Itai Itai disease is associated with long term exposure to a particular heavy metal.
• Exposure occurred mainly through contaminated rice and water in certain regions.
• The options include several heavy metals known for various health effects.
• We assume standard textbook descriptions of major pollution related diseases.

Concept / Approach:
Itai Itai disease was first reported in Japan and is primarily linked to chronic cadmium poisoning. Cadmium from mining and industrial discharge contaminated rivers and rice fields. Over many years, people consuming contaminated rice suffered severe damage to bones and kidneys, leading to extreme pain in the joints and spine. Other metals like mercury, lead, and chromium cause different classical syndromes, but the name Itai Itai is specifically associated with cadmium.

Step-by-Step Solution:

Verification / Alternative check:
Basic environmental chemistry references describe several famous pollution incidents. Minamata disease in Japan is due to methyl mercury poisoning from industrial discharge into Minamata Bay. In contrast, Itai Itai disease occurred mainly in the Jinzu River basin due to cadmium pollution. The name Itai Itai, meaning "ouch ouch" in Japanese, reflects the intense bone pain caused by cadmium induced osteomalacia and osteoporosis. These associations are consistently reported across textbooks, which confirms that cadmium is the correct answer.

Why Other Options Are Wrong:

• Nickel: Can cause dermatitis and allergic reactions but is not linked to the named Itai Itai disease.
• Chromium: Especially hexavalent chromium is toxic and carcinogenic but associated with different health issues.
• Mercury: Responsible for Minamata disease, not Itai Itai, and mainly affects the nervous system.
• Lead: Causes lead poisoning, particularly in children, leading to neurological and developmental problems, but not Itai Itai disease.

Common Pitfalls:
Students may mix up the names of pollution related diseases and the metals involved, especially when revising quickly. Confusing Minamata disease with Itai Itai disease is common. A helpful way to remember is to link Minamata with mercury and fish consumption, and Itai Itai with cadmium and severe bone pain from contaminated rice. Organising these associations in a small table during revision can reduce confusion.

Final Answer:
The metal mainly responsible for Itai Itai disease is Cadmium.