Are you protecting participants' data?
Nobody except the research team should have access to the data or be able to find out participants’ identities. It is often impossible to provide complete anonymity, as many methods require direct contact with the person conducting the research. Ensuring that responses are kept confidential – changing names to identification numbers, for example – can help you deal with this.
Where will the research take place? Will other people be within earshot? How many people are in this population group? Could their story be identifiable to others because there are only one or two people in this situation? If you believe this could happen, either choose to not carry out the research with this particular person, or agree you will not use any data that could identify them to others.