Abstract
<jats:p> Air particulate matter (PM) standards rely heavily on epidemiological and toxicological endpoints, in addition to failing to consider regional differences and population sensitivity. Using rat's natural intelligence, this work has pioneered a PM exposure threshold measurement protocol by quantifying the amount of PM-spiked water consumed and then extrapolating them to human exposure at the time of rats' avoidance. Using the method, the no-observed health effect limits of ambient PM for representative cities: Beijing, Hohhot, Guangzhou, Xi'an, and Taiyuan were sought as 8.54 (7.57, 9.50) μg/m <jats:sup>3</jats:sup> , 3.88 (3.45, 4.31) μg/m <jats:sup>3</jats:sup> , 3.39 (3.15, 3.63) μg/m <jats:sup>3</jats:sup> , 1.46 (1.27, 1.66) μg/m <jats:sup>3</jats:sup> , and 0.70 (0.46, 0.94) μg/m <jats:sup>3</jats:sup> , respectively. PM standards as determined by rats for some cities here are close to 5 μg/m <jats:sup>3</jats:sup> as recommended by World Health Organization. Interestingly, these exposure thresholds appear before rats develop pathological damages, and such limits for hypertensive rats groups were observed further lower. The PM water avoidance by rats was also accompanied by changes measured here in their breath-borne volatile organic compounds (VOCs), gut microbiota, metabolic enzymes, inflammation, oxidative stress, and pathologies for different cities. This work has pioneered the use of animal intelligence (AI) in developing sensitive PM standard for different cities, and using rats' intelligence, different city PM standards can be readily developed for maximizing air pollution control cost-effectiveness. </jats:p>