Strengths and limitations
As explained in Laursen et al. 2021 [The present study also has limitations. First, exposure to indoor and ambient pollution between the days of the experiments might impact the results, as participants were left unattended in their homes with no instructions regarding behaviour except for not using tobacco products and not taking medicine. However, due to the crossover design and randomization of the exposures, the activities of participants in the hours and days before the exposure sessions are expected to cause random effects, thereby attenuating the exposure-outcome association. Secondly, in the case of delayed effects, the health effects of cooking and candle burning may have been underestimated in the present study. However, as the exposures are not assumed to be receptor-mediated as, e.g. endotoxin showing systemic effects persisting for weeks [