Psychological outcomes from a citizen science study on microplastics from household clothes washing

Abstract

Microplastic pollution in the form of synthetic microfibers is an increasing concern to human and ecological health, and household clothes washing is a major contributor to microplastic emissions. Consumer choices and washing behaviors could reduce this pollution, yet the psychological and behavioral drivers of these actions remain unknown. We present a pre-registered, three-month citizen science project in which Dutch residents used microfiber-capturing laundry bags at home. The citizen scientists completed pre- and post-study surveys of psychological factors such as identity, norms, perceived responsibility, and intentions, as well as washing behaviors like load size and washing temperature. After the study, citizen scientists increased modestly in problem awareness and perceived responsibility, but there were no significant changes in identity, personal norms, social norms about sustainability, perceived behavioral control, or intentions to use a laundry bag. To assess generalizability, we also compared the citizen scientists to a control sample of urban Dutch residents. The washing behaviors were weakly or uncorrelated with demographics or with psychological factors, suggesting that interventions on washing behaviors might focus on habits and skill development rather than trying to increase pro-environmental motivation. These results also suggest that interventions tested in citizen scientists may translate better to other populations than was previously suggested. Citizen science is a viable method for studying household washing under real-world conditions and provides insights for designing targeted behavioral interventions.

Fig. 1. The Guppy Friend® Laundry Bag.

Fig. 2. Participant residence from Dutch postcodes. Note. 13 participants of the control survey (Urban Dutch) (n = 814) did not provide postcodes.

Fig. 3. (a)Pre-registered participation outcomes with pre-post changes (p_s < 0.05). Note. The red dots indicate means, the boxes indicate interquartile ranges, and the lines in the boxes indicate medians. The points are jittered and partially transparent to better show the distributions. (b) Pre-registered participation outcomes without pre-post changes (p_s ≥ 0.05). Note. The red dots indicate means, the boxes indicate interquartile ranges, and the lines in the boxes indicate medians. The points are jittered and partially transparent to better show the distributions.

Fig. 4. Spearman correlations between psychological variables and Intention to use laundry bags and video-watching in the control survey (Hypothesis 3) (N_s = 683-814). Note. The boxes represent the interquartile range of correlation coefficients, and each solid line represents the median correlation. The dotted lines indicate that correlations were significant at p < 0.05 (|r_s| ≥ 0.07). 68.6% of participants stayed on the page of the video for less than 15 seconds. The distribution of video-watching is shown in Fig. S1, and the floor effect may limit correlation size.

Fig. 5. Correlations between Psychological Variables and Washing Behaviors in the Control Survey (Urban Dutch) (Ns = 702-814). Note. The boxes represent the interquartile range of correlation coefficients, and each solid line represents the median correlation. The dotted lines indicate which correlations were significant at p < 0.05: |r_s| ≥ 0.07.