Indoor mould is known to damage respiratory health, including worsening exacerbations and increasing occurrence of asthma. This is a prevalent issue and the number of people exposed to indoor mould exposure has been increasing (from 18% to 50%). This exposure is at risk of increasing with further climate change,for example with increasing numbers of floods occurring there will be a worsening of indoor mould growth. Previous studies have shown that early-life exposure to risk factors, such as air pollution, are associated with reduced lung growth and lower FEV1 as well as detrimental lung function trajectories; some of these trajectories are characterised by earlier onset respiratory disease and associated with premature death. This study will investigate the early life influence of indoor mould on lung function trajectories up to 24 years old (i.e. nearing respiratory physiological plateau) using data from the ALSPAC population based birth cohort.