3.1. Outdoor exposure
Outdoor formaldehyde concentrations for several Chinese cities are
detailed in Table 2. China's large cities have formaldehyde levels similar
to cities in other developing countries such as Egypt,Mexico, and Brazil,
but significantly higher than those of large cities in developed countries
like Japan, Sweden and Canada (Zhang et al., 2009). Typical of most
countries in the world, outdoor air standards are unregulated in China.
Although research exclusively targeting China's outdoor rural formaldehyde
levels has been limited, several indoor studies have measured
rural outdoor concentration ranges of 10 to 20 μg/m3 (Liu et al.,1993; Xu
et al., 2008).