Problem 17 - A Complete Resource Book in Chemistry for JEE Main

Question

Minamata disease is caused due to the presence of \(\ldots \ldots\) in water. (a) \(\mathrm{Hg}\) (b) \(\mathrm{Pb}\) (c) \(\mathrm{Cd}\) (d) As

Step-by-Step Solution

Answer

Minamata disease is caused by \( \mathrm{Hg} \). (Option a)

Step 1: Identify the Context of Minamata Disease

Minamata disease is a neurological syndrome. It was discovered in Minamata city, Japan, and is associated with industrial pollution.

Step 2: Determine the Chemical Cause

Research and historical records show that Minamata disease resulted from mercury poisoning. Industrial waste containing mercury was dumped into Minamata Bay by a chemical factory, leading to bioaccumulation in shellfish and fish which, when consumed, caused the disease.

Step 3: Match with Given Options

Compare the identified cause (mercury) with the options provided: (a) \( \mathrm{Hg} \) for mercury, (b) \( \mathrm{Pb} \) for lead, (c) \( \mathrm{Cd} \) for cadmium, and (d) As for arsenic. Mercury corresponds to option (a), \( \mathrm{Hg} \).

Key Concepts

Mercury Poisoning

Mercury poisoning is a severe health problem caused by exposure to mercury, a toxic heavy metal. Mercury can be found in various forms: elemental (metallic), inorganic compounds, and organic compounds like methylmercury. Each form has different levels of toxicity and ways of entering the body.
When mercury is released into the environment, it can come in contact with wildlife and people. Humans may be exposed to mercury through several ways:

• Ingesting contaminated fish and shellfish
• Inhaling mercury vapor
• Through skin contact with mercury-containing products

Methylmercury, the most toxic form, often accumulates in the food chain. It affects the nervous system, causing symptoms like:

• Numbness in hands and feet
• Muscle weakness
• Impaired vision and hearing
• Memory problems

Preventing mercury poisoning involves reducing industrial emissions, monitoring fish consumption, and using alternatives to mercury in household and industrial products.

Bioaccumulation

Bioaccumulation is a process where toxins like mercury build up in the bodies of living organisms over time. This occurs because these substances are absorbed faster than they are metabolized or excreted. In the case of methylmercury, small organisms like plankton absorb it from their environment. Larger animals, such as fish, eat multiple contaminated organisms, leading to higher concentrations of mercury in their bodies over time.
This is particularly dangerous in marine ecosystems, as mercury levels increase significantly up the food chain:

• Small fish consume the contaminated plankton.
• Larger fish eat smaller fish, accumulating more mercury.
• Humans consume top predators like tuna or shark, thus ingesting high mercury levels.

Understanding bioaccumulation helps in managing and controlling the spread of toxic substances in the environment. Strategies include regulating emissions and discharges that contain mercury and advising communities about safe consumption levels of certain fish.

Industrial Pollution

Industrial pollution is the release of harmful substances into the environment as a result of industrial activities. This pollution can affect air, soil, and water, leading to significant environmental and health problems. Mercury is a common pollutant in industrial waste, particularly from:

• Chemical manufacturing plants
• Coal-fired power plants
• Gold mining operations

Once released, mercury can travel great distances through the air and water, entering ecosystems far from the original source. The Minamata tragedy is a prime example of the disastrous effects of industrial pollution, where mercury was irresponsibly discharged into local waters.
Preventing industrial pollution requires strict enforcement of environmental regulations, adoption of cleaner technologies, and international cooperation to control cross-border pollution. Ensuring industries comply with waste treatment standards can help reduce the harmful impact on our planet and health.