The correct option is "1 and 4 only" because, according to WHO Air Quality Guidelines, the recommended limits for PM2.5 are indeed that the 24-hour mean should not exceed 15 µg/m³ and the annual mean should not exceed 5 µg/m³, aligning with the public health goal of minimizing respiratory and cardiovascular impacts. Additionally, excessive ozone levels in the air can exacerbate respiratory conditions such as asthma due to ozone's potent oxidizing properties, which irritate the airways. In contrast, statement 2 is inaccurate as the highest levels of ozone typically occur during hot, sunny conditions rather than inclement weather, and statement 3 is misleading; while PM10 can penetrate deeply into the respiratory system, PM2.5 is primarily responsible for entering the bloodstream due to its smaller size.