Inorganic mercury causes relatively minor CNS effects because it does not cross the blood–brain barrier.

Inorganic mercury causes relatively minor CNS effects because it does not cross the blood–brain barrier.

• A. True
• B. False
• C. Not sure
• D. Cannot determine

Answer: (A)

The key idea is that entry into the brain is governed by the chemical form of mercury. The blood-brain barrier acts as a selective shield, and inorganic mercury exists mainly as ionic, water-loving species that are not very lipophilic. Because of that, inorganic mercury doesn’t cross into the brain readily, so CNS effects are limited or relatively minor. In contrast, organic mercury compounds, like methylmercury, are lipophilic and use transport pathways to enter the brain easily, leading to more pronounced CNS toxicity. So the statement is true: inorganic mercury generally causes only small CNS effects because it doesn’t cross the blood-brain barrier well. Keep in mind that extremely high exposures or situations where the barrier is immature or damaged can alter this, but the usual expectation is limited CNS impact from inorganic mercury.

The key idea is that entry into the brain is governed by the chemical form of mercury. The blood-brain barrier acts as a selective shield, and inorganic mercury exists mainly as ionic, water-loving species that are not very lipophilic. Because of that, inorganic mercury doesn’t cross into the brain readily, so CNS effects are limited or relatively minor. In contrast, organic mercury compounds, like methylmercury, are lipophilic and use transport pathways to enter the brain easily, leading to more pronounced CNS toxicity. So the statement is true: inorganic mercury generally causes only small CNS effects because it doesn’t cross the blood-brain barrier well. Keep in mind that extremely high exposures or situations where the barrier is immature or damaged can alter this, but the usual expectation is limited CNS impact from inorganic mercury.