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.
A reader might infer from this passage that __________.
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A
most dangerous lead exposure happens later in life
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B
doctors are concerned about what happens to the brain during aging
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C
shinbones are good indicators of many health ailments or conditions
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D
blood tests are the best way to measure individuals’ lifetime lead exposure
A reader might infer that doctors are concerned about brain health during aging, as evidenced by Dr. Schwartz's research connecting early toxin exposure to cognitive decline in senior years.
A) most dangerous lead exposure happens later in life
This contradicts the passage, which emphasizes exposure "in younger years" affecting "senior years"—suggesting early-life exposure carries long-term consequences rather than late-life exposure being most dangerous.
B) doctors are concerned about what happens to the brain during aging
Dr. Schwartz explicitly investigates how "environmental exposures like lead" might explain "what has been called normal aging," with research focusing on "mental functions, including verbal and visual memory and language ability" in aging populations—demonstrating clear professional concern for cognitive aging.
C) shinbones are good indicators of many health ailments or conditions
The passage mentions shinbone testing only for lead accumulation—providing no evidence shinbones indicate multiple health conditions. This overgeneralizes a single diagnostic application.
D) blood tests are the best way to measure individuals' lifetime lead exposure
This directly contradicts the passage, which states blood tests reveal "recent, not lifelong, exposure," while shinbone testing measures accumulated lifetime exposure—making blood tests inferior for this specific purpose.
Conclusion
Valid inferences extend logically from textual evidence without contradicting stated facts. Dr. Schwartz's research focus on aging brain function provides clear evidence of medical concern for cognitive health during aging—making this the only supportable inference.