Table 1 Survey questions and items

Personal area of interest

Generally speaking, how interested are you personally in protecting the natural environment compared to protecting human health?

7-point rating scale from 1 (I am primarily interested in protecting the natural environment), 4 (I am equally interested in protecting both) to 7 (I am primarily interested in protecting human health)

Risk perception: worry

Partly adapted from Special Eurobarometer (2020) [10] & Van der Linden (2015) [45]

How worried, if at all, are you about the current impact of everyday products made of plastic/ microplastics on the natural environment/ human health?

7-point rating scale from 1 (Not at all worried) to 7 (Extremely worried), and 99 (Don’t know)

If you have indicated that you are worried for any of the above, please briefly state what impacts you are specifically worried about. (optional)

Open-ended question

Quality of evidence perception

Adapted from Pahl, Richter & Wyles (2022) [43]

In your opinion, how good is the current state of the microplastics evidence regarding the impact on the natural environment/ human health?

7-point rating scale from 1 (Very poor) to 7 (Very good), and 99 (Don’t know)

Risk perception: likelihood and severity of microplastics impacts on the natural environment and human health

Adapted from Van der Linden (2015) [45]

How likely do you think it is that microplastics from the following sources are having a negative impact on the natural environment/ human health?

7-point rating scale from 1 (Not likely at all) to 7 (Extremely likely), and 99 (Don’t know)

How severe do you think any negative impacts of microplastics from the following sources are for the natural environment/ human health?

7-point rating scale from 1 (Not severe at all) to 7 (Extremely severe), and 99 (Don’t know)

In your opinion, are there other sources of current microplastics pollution that are not covered above? (optional)

Open-ended question

In your opinion, is there a particular microplastics source which has the most impact on the natural environment and human health? Please state briefly why. (optional)

Open-ended question

Solution perception: effectiveness and feasibility

How effective do you think each potential solution might be in reducing current microplastics pollution?

7-point rating scale from 1 (Not effective at all) to 7 (Extremely effective), and 99 (Don’t know)

How feasible do you think each potential solution might be to reduce current microplastics pollution?

7-point rating scale from 1 (Not feasible at all) to 7 (Extremely feasible), and 99 (Don’t know)

In your opinion, are there other solutions (technical, behavioural or policy related) that could reduce current microplastics pollution that are not covered above? (optional)

Open-ended question

In your opinion, what is the most effective and feasible solution to reduce current microplastics pollution? Please explain briefly why. (optional)

Open-ended question

Socio-demographics

How would you describe your gender?

Nominal Scale: Male/Female/ Non-Binary/ Prefer not to say

How old are you?

Metric Scale

What is your country of residence?

Open-ended question

Expert identification

Partly adapted from Provencher et al. (2020) [7]

How would you describe your career stage?

Ordinal Scale:

Early/ Mid/ Established/ Prefer not to answer

Do you participate in the field of plastic research?

Nominal Scale:

Yes/ No/ Prefer not to answer

If yes:

For how many years?;

How is your research funded primarily?;

Do you work on microplastics specifically?;

In what discipline primarily?;

In what geographical region have you studied plastic? (optional)

If no:

How, if at all, is your position related to plastic?

Funding:

Public/ Industry /Both/ Other/ Prefer not to answer;

Microplastics research: Yes/No/ Prefer not to answer;

Other items: Open-ended question