300. Tio2
P1 - Researchers are testing construction materials to see how well they can fight pollution
P2 - TD can clear the air because it's a photocatalyst. It turns inorganic and organic compounds into molecules that can be washed away with the rainfall. But the width of the pollutionfighting form is about 7nms.
P3 - Since the early 1970s, scientists have exploited the compound to kill bacteria on hospital surfaces and to treat contaminated water. Fighting NO on the street is the latest twist. E.g in HK.
JCMY compliments the efficiency and adds the TD is a catalyst, it could last forever.
P4 - Some problems:
CK - it doesn't absorb sunlight.
AH - only 3% of sunlight falls into the range needed for it to work.
RA - boosted the efficiency to 10% but it is still a small %
P5 - And paving roads and coating buildings with TD could be expensive.
Yu: the countries with the most air pollution which need it most but can't afford it.