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In the context of WHO Air Quality Guidelines, consider the following statements :
1. The 24-hour mean of PM2.5 should not exceed 15 μg/m3 and annual mean of PM2.5 should not exceed 5μg/m3.
2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather.
3. PM10 can penetrate the lung barrier and enter the bloodstream.
4. Excessive ozone in the air can trigger asthma.
Which of the statements given above are correct ?
(a) 1, 3 and 4
(b) 1 and 4 only
(c) 2, 3 and 4
(d) 1 and 2 only



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Statement 2 is not correct: Ozone levels are typically highest in presence of sunlight. Inclement weather means unpleasant weather with cold wind and rain. So, Ozone pollution will low during inclement weather. C and D eliminated.

Statment 3 is not correct: Particular matter 2.5 (PM2.5) and not PM10) can can penetrate the human lung barrier and enter the blood system. So A is eliminated. Therefore by elimination the answer is B.


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