Development and preliminary validation of a household laundering Behaviour questionnaire and framework for estimating potential washing-machine-derived microfibre release through household wastewater pathways: implications for aquatic environments

Abstract

Household washing machines release synthetic textile-derived microfibres into wastewater systems. Yet, standardised questionnaires assessing household laundering practices linked to microfibre emissions remain limited. This study developed and preliminarily evaluated a household microfibre emission behaviour questionnaire and proposed a framework for estimating potential washing-machine-derived microfibre release through Malaysian household wastewater pathways. The questionnaire was developed through literature-informed domain identification, expert review, content and face validity assessments, guided by an integrated Knowledge–Attitudes–Practices and Theory of Planned Behaviour framework. Content validity was assessed by 10 experts and face validity by 20 adult public respondents, followed by pilot testing among 43 Malaysian adults. The revised questionnaire comprised 58 items across six domains, plus one laundering-frequency input item. Internal consistency was assessed for 48 knowledge and Likert-scale items, while 10 barriers were analysed descriptively as binary indicators. Content and face validity index values ranged from 0.96 to 0.98. Preliminary internal consistency was acceptable, with a KR-20 value of 0.885 for the knowledge domain and Cronbach’s alpha values ranging from 0.817 to 0.849 across the Likert-scale domains. The proposed equation estimates annual washing-machine-derived microfibre release through laundry-wastewater pathways. It incorporates laundering frequency, household numbers, washing-machine penetration, per-cycle release and sewered, septic and unmanaged wastewater fractions. Other behavioural indicators can refine the framework as empirical coefficients become available. The framework was neither calibrated nor validated and does not estimate environmental transport or confirmed aquatic loading. Together, these components provide a context-specific approach to assessing laundering behaviours and potential microfibre release in Southeast Asia.