Minamata disease is a severe nervous system disorder caused in humans by eating fish that have been polluted with which toxic metal?

Introduction / Context:
This question is based on environmental science and public health. Minamata disease is a well known example used to illustrate the dangers of industrial pollution and biomagnification of toxic substances in aquatic food chains. Knowing the metal responsible helps students connect pollution, ecology, and human health.

Given Data / Assumptions:
- Minamata disease is described as a nervous disorder. - It is linked to eating polluted fish. - The options list several common metals: iron, mercury, lead, and nickel.

Concept / Approach:
Minamata disease was first identified in Minamata Bay in Japan, where industrial discharge of methyl mercury into the water contaminated fish and shellfish. People who consumed this seafood developed severe neurological symptoms. The key concept is biomagnification of mercury in the food chain, which led to high doses in humans.

Step-by-Step Solution:
1. Recall that Minamata disease is associated with industrial mercury pollution. 2. Mercury enters water bodies, is converted to methyl mercury, and accumulates in fish. 3. Humans who eat contaminated fish get high levels of methyl mercury. 4. This mercury especially damages the nervous system, causing tremors, numbness, and cognitive problems. 5. None of the other listed metals match the famous Minamata incident. 6. Therefore, the correct answer is mercury.

Verification / Alternative check:
Environmental science textbooks and case studies on Minamata Bay consistently mention mercury as the cause of Minamata disease. The disease is often used as a classic example of mercury poisoning through the aquatic food chain.

Why Other Options Are Wrong:
Iron: An essential nutrient metal and not the primary cause of Minamata disease. Lead: A toxic heavy metal, but it is associated with different disorders, such as lead poisoning, not Minamata disease. Nickel: Can cause allergies and other issues but is not linked to Minamata disease.

Common Pitfalls:
A common error is to mix up heavy metals and assume that any of them might be responsible. Students should remember Minamata disease specifically as a case of mercury contamination and biomagnification. Linking the name Minamata with mercury will help recall the answer quickly in exams.

Final Answer:
Minamata disease is caused by eating fish polluted with the toxic metal Mercury.