Extract:
Toxins and Your Health
Lie out in the sun too much today, and get skin cancer 20 years from now. Smoke too many cigarettes now, and get lung cancer decades down the road. Now there is potentially a third danger to add to this list: be exposed to too much lead, pesticides, or mercury now and have your aging brain become seriously confused during your senior years.
“We’re trying to offer a caution that a portion of what has been called normal aging might in fact be due to ubiquitous environmental exposures like lead,” says Dr. Brian Schwartz of Johns Hopkins University. “The fact that it’s happening with lead is the first proof of the principle that it’s possible.”
A new area of medical research is one that studies how exposure to toxic elements in younger years can result in serious health problems in senior years. It is difficult to research these problems because the only way to do so is to observe people over many years.
Physicians test for lead amounts by seeing how much has accumulated in a person’s shinbone. Testing the blood also often reveals amounts of lead, but that is a sign of recent, not lifelong, exposure. The higher the lifetime lead dose, according to the study, the worse the performance of mental functions, including verbal and visual memory and language ability.
What is the main idea of the passage?
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A
Environmental toxins may have dire health effects over time.
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B
Of three toxins studied, lead has the worst effect on health.
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C
Toxins may accumulate in the bones of older patients.
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D
Johns Hopkins University has discovered a new use for lead.
The main idea is that environmental toxins may have dire health effects over time, connecting early exposure to delayed consequences through the lead research example.
A) Environmental toxins may have dire health effects over time
This captures the passage's central thesis introduced through parallel structure (sun/skin cancer, smoking/lung cancer) then extended to toxins/brain aging. Dr. Schwartz's research demonstrates how "exposure to toxic elements in younger years can result in serious health problems in senior years," with evidence linking lifetime lead dose to cognitive decline.
B) Of three toxins studied, lead has the worst effect on health
The passage mentions lead most extensively only because it's Dr. Schwartz's research focus, not because it's compared against pesticides or mercury as most harmful. No comparative severity assessment appears.
C) Toxins may accumulate in the bones of older patients
This describes a research methodology detail (shinbone testing) rather than the central message about long-term health consequences of environmental exposure.
D) Johns Hopkins University has discovered a new use for lead
The research investigates lead's harmful effects, not beneficial applications. No "new use" is discussed; the focus is on understanding lead's role in cognitive aging.
Conclusion
Main ideas must encompass a passage's comprehensive focus, not isolated details or institutional affiliations. Option A successfully integrates the delayed-consequence framework with specific research evidence about toxins affecting aging brains.