III. Blank-filling : (每格1分，共10分)

Researchers studied exposure to polycyclic aromatic hydrocarbons, or PAHs. They found that(16) exposure to these compounds was tied to changes in the structure of offspring’s brains and to intellectual deficits and behavioral problems in childhood.

The researchers measured PAH (17) in the air and in the blood and urine of 40 mothers in their third (18) of pregnancy, as well as in their children’s urine. They followed the children until they were 7 to 9 years old, (19) M.R.I. exams on their brains. The results are in JAMA Psychiatry.

The higher the exposure to PAHs, the more reductions the children had in the white matter surface of the left hemispheres of their brains. The amount of damaged white matter (20) directly with higher scores on measures of symptoms of attention deficit (21) disorder and other behavioral problems. Higher exposure to PAHs and white matter (22) were also associated with lower scores on tests of (23) speed, the ability to take in new information and respond to it.

Critically, as noted, PAHs have been identified as (24), and are considered pollutants of concern for the potency of potential (25) health impacts; the same holds true of their presence at significant levels over time in human diets.