Perceptions, preferences, and behavioral change to mitigate microplastics pollution

Last registered on July 25, 2025

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Pre-Trial

Trial Information

General Information

Title

Perceptions, preferences, and behavioral change to mitigate microplastics pollution

RCT ID

AEARCTR-0016371

Initial registration date

July 18, 2025

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published

July 25, 2025, 11:32 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

Country

United States of America

Region

Primary Investigator

Name

Jacob Waugh

Affiliation

Indiana University - Bloomington

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Other Primary Investigator(s)

PI Name

Emi Uchida

PI Affiliation

University of Rhode Island

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PI Name

Katherine Westerman

PI Affiliation

University of Rhode Island

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PI Name

Sonia Refulio Coronado

PI Affiliation

University of Rhode Island

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PI Name

Annalise Wabler

PI Affiliation

Ohio State University

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Additional Trial Information

Status

In development

Start date

2025-07-21

End date

2025-08-21

Keywords

Behavior, Environment & Energy

Additional Keywords

Economics, Nudge, Microplastics

JEL code(s)

Q51, Q52, Q53

Secondary IDs

Prior work

This trial does not extend or rely on any prior RCTs.

Abstract

Synthetic microfibers represent one of the most prevalent sources of marine microplastic pollution, with much of the pollution linked to the laundering of synthetic-fiber based clothing. Many environmental pollution problems offer limited opportunities for consumers and households to play a material role in mitigating pollution; however, with new sustainable laundry technology (i.e., water filters, washing bags, laundry balls), consumers can significantly reduce their household microfiber emissions through various cost effective, low effort products. Currently, consumer adoption of such products remains low. It is well established in the behavioral science and behavioral economics literatures that informational nudges and message frames are effective tools for promoting behavioral change across several domains. Few studies exist linking nudges and microplastic-generating behaviors, and, to date, no known study applies nudges to laundering behavior in a microplastic context. This study evaluates how informational nudges and message framing affect (1) consumer's intent to purchase, willingness-to-pay, and preferences for sustainable laundry products and (2) how individuals value municipal wastewater treatment improvements to reduce microfiber pollution at the societal level, as measured by a contingent valuation question. An online survey instrument will provide subjects with varying levels of information about microplastic pollution, as well differing message frames, before assessing key intention and willingness measures for laundry products. This study provides both hypothetical product choices, based on current market options, and market-like choices. The study aims to generate evidence on how non-coercive behavioral interventions can encourage individual action and collective support for products and policies mitigating the ecological and human health effects of microfiber pollution.

External Link(s)

Registration Citation

Citation

Refulio Coronado, Sonia et al. 2025. " Perceptions, preferences, and behavioral change to mitigate microplastics pollution." AEA RCT Registry. July 25. https://doi.org/10.1257/rct.16371-1.0

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Experimental Details

Interventions

Intervention(s)

This study conducts nudging interventions through an online survey to measure the effects of informational and framed nudge interventions on consumers' attitudes towards and intentions-to-purchase sustainable laundry products designed to reduce microplastic pollution. Our study also measures subjects' willingness to pay for such laundry products and their willingness to pay (through property taxes) for improvements to municipal wastewater treatment facilities to reduce microplastic pollution at the societal-level.

Our intervention varies between treatment arms in the level and framing of microplastic information presented to subjects. Information varies from basic microplastic definitions in the control group to more detailed information about microplastic sources, dangers, and mitigation activities in treatments 1 and 2. Treatment 2 also introduces a collective action frame to the microplastic information.

Intervention (Hidden)

The intervention presents microplastics information depending on a randomized group assignment into the control, treatment 1, or treatment 2 group. Group assignment is evenly distributed.

Those in the control group are considered the "No information" group, receiving only a definition of microplastics (MPs) and microfibers, adapted from the Oxford English Dictionary entries.

Treatment 1 receives an infographic detailing the prevalence of MPs, locations where MPs have been found, common household sources of MP pollution, a statement indicating synthetic textiles as a leading source of MP pollution, and potential methods to reduce MP emissions from laundry.

Treatment 2 receives a similar infographic with all of the same details as Treatment 1. In addition, Treatment 2 offers a collective action messaging frame, established by providing three examples of ways governments and industry are also working to reduce MPs and messaging that invokes feelings of collective action (i.e., "Join the movement"). Treatment 2 builds on O’Donnell and Guidry’s (2022) findings that a sense of collective action and shared responsibility can promote pro-environmental behaviors.

Intervention Start Date

2025-07-21

Intervention End Date

2025-08-21

Primary Outcomes

Primary Outcomes (end points)

1) Intent to purchase sustainable laundry products
2) Willingness to pay for sustainable laundry products
3) Willingness-to-pay for municipal wastewater treatment upgrades

Primary Outcomes (explanation)

1) Discrete choice questioning for each tested product
2) Measured using a single-bounded contingent valuation question
3) Measured using a single-bounded contingent valuation question

Secondary Outcomes

Secondary Outcomes (end points)

1) Environmental attitudes
2) Microplastic knowledge
3) Ascription of environmental responsibility

Secondary Outcomes (explanation)

1) Measured through a brief set of questions measuring feelings of environmental responsibility, environmental self-efficacy, and pro-environmental behaviors
2) Measured with a single self-reported question on prior familiarity with microplastics.
3) Measured with a single question asking respondents to assign responsibility for addressing microplastic pollution to various groups (e.g., local governments, industry)

Experimental Design

We initially branch respondents based on screening questions gauging their access to a washing machine they can modify and their current use of a microplastic mitigating laundry product. Those who already employ sustainable laundry products will not be randomly assigned and will proceed directly to the societal contingent valuation question. Subjects are randomly and evenly assigned to control, treatment 1, and treatment 2.

Experimental Design Details

Initially, we screen respondents to determine (a) if they have access to a washing machine they can modify and (b) if they already use a laundry product designed to reduce microfiber shedding or capture microfibers. Those without access to a washing machine they can modify will not receive questions about washing machine microplastic filters, but will still receive questions about the laundry ball and washing bag. Those who already own microplastic mitigation tools will proceed past the information treatments and begin the substantive part of the survey at the societal contingent valuation question.

Those who are eligible to receive the treatments are randomly and evenly assigned to control, treatment 1, or treatment 2. After randomization, subjects are asked to indicate their intent to purchase and willingness to pay for three (or 2 if in the “cannot modify” group) individual products based on real market options. Following questions regarding individual products, subjects encounter a “market choice” question, where we have added the real market price and branding to all three (or 2) products. Respondents are asked to indicate their preferred product, if any.

Randomization Method

Randomized by Qualtrics survey software

Randomization Unit

Individual

Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters

N/A

Sample size: planned number of observations

420 individuals

Sample size (or number of clusters) by treatment arms

By nature of our experimental design, we cannot be sure of the number of respondents per treatment arm because an unknown proportion of our sample will be screened out of the random treatment process. However, the number of subjects in each treatment arm will be evenly distributed regardless of the total number of treated subjects.

Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Conducted an a priori, ANOVA, fixed effects, omnibus, one-way statistical test. Parameters: Effect size f = 0.25 (moderate effect) Alpha error probability = 0.05 Power = 0.8 3 groups Minimum sample size of 159 (53 per group) Parameters: Effect size f = 0.25 (moderate effect) Alpha error probability = 0.05 Power = 0.8 3 groups Minimum sample size of 159 (53 per group)

Supporting Documents and Materials

IRB