Residential building materials: An important source of ambient formaldehyde in mainland China.

• This study is the first to investigate indoor formaldehyde contribution to ambient. • Residential building materials are a significant source of ambient formaldehyde. • The share of residential emissions to 81 anthropogenic sources was 6.66% (rank 6th). • Residential emission intensities were higher in more urbanized areas. • Building density, building materials, T and RH are influencing factors of emission. This study investigates the contribution of formaldehyde from residential building materials to ambient air in mainland China. Based on 265 indoor field tests in 9 provinces, we estimate that indoor residential sources are responsible for 6.66% of the total anthropogenic formaldehyde in China's ambient air (range for 31 provinces: 1.88–18.79%). Residential building materials rank 6th among 81 anthropogenic sources (range: 2nd–10th for 31 provinces). Emission intensities show large spatial variability between and within regions due to different residential densities, emission characteristics of building materials, and indoor thermal conditions. Our findings indicate that formaldehyde from the indoor environment is a significant source of ambient formaldehyde, especially in urban areas. This study will help to more accurately evaluate exposure to ambient formaldehyde and its related pollutants, and will assist in formulating policies to protect air quality and public health. [ABSTRACT FROM AUTHOR]