The Plastic Exposure Reduction Transforms Health Trial

Many plastic products contain endocrine disrupting chemicals, such as bisphenols and phthalates (referred to as plastic-associated chemicals or PAC), which leach out from everyday use and enter the human body. Food contaminated from packaging or with plastic particles, personal care and cleaning products may be sources of PAC which can be inhaled or absorbed through the skin. The fundamental premise underpinning the research is that exposure to PAC, combined with genetic and lifestyle factors, creates chronic and systemic inflammation that underpins cardiometabolic conditions.

This randomized controlled trial aims to demonstrate whether decreasing exposure to plastic and PAC will reduce urinary excretion of PAC and improve cardiometabolic biomarkers in people with cardiometabolic risk factors.

Participants that have consented and passed health screening (N=60) will be randomized to one of two parallel groups, to receive a 4-week low plastic intervention in their homes with the support of registered dietitians.

• Group 1 (N=30): low plastic intervention group
• Group 2 (N=30): control/no intervention group

All participants will attend four in-person clinic appointments, one during screening, and three during the intervention (Visit 1: day 0, baseline; Visit 2: day 16, midpoint; and Visit 3: day 29, post intervention), of up to two hours duration each. In addition, participants will have a video/phone appointment between screening and Visit 1.

The day before and after the video/phone appointment, participants will be asked to collect urine, stool and nasal washing samples and send them back the day after their video/phone appointment. At the end of the video/phone appointment, eligible and willing participants will be invited to continue to the intervention study and randomized into either the intervention or control group. At the video/phone appointment, participants from Group 1 will order their food and personal care products. The researchers will send the order to a local meal service delivery who will order, pay for, package, and deliver the approved food to the participants' homes in insulated boxes. Delivery of approved products to participants' homes will take place the day before the intervention begins, and at other pre-determined timepoints throughout the study, as required. Samples of food products will be frozen for retrospective testing for PAC, if exposure testing indicates contamination from an unexpected source. Participants from Group 1 will use only non-plastic cooking utensils provided by the researchers and follow guidance concerning the preparation of their food. Participants from Group 1 will use only personal care and cleaning products supplied by the research team. Personal care products include, but are not limited to shampoo, conditioners, face moisturizers, cleansers, serums, make-up and sunscreens, deodorant, tampons and applicators. Participants will be supplied with a comprehensive schedule, and instructions for the 4-week intervention.

All participants will be asked to collect urine, stool, and nasal washing samples on days -1, 8, 15, 22 and 28 of the intervention period, and return them at the clinic visits. During the clinic visits, participants will have fasting blood sample taken, complete the sociodemographic questionnaire, a physical activity assessment using the International Physical Activity Questionnaire (IPAQ - Short Form), the 24-hr personal care product recall questionnaire, the plastic-associated chemicals questionnaire and be interviewed by a member of the research team to complete a 24-hour diet recall - plastic exposure (24DR-PE) of food consumed, and how it was stored prepared, and consumed. The 24DR-PE will facilitate assessments of deviations from the protocol, and enable the assessment of energy, macro and micronutrient intake.

For intervention adherence the following assessment tools will be employed:

24-hour dietary recall - plastic exposure interview (24DR-PE): This assessment is a researcher-administered, computer-assisted, 24-hour dietary recall interview. The method assesses dietary intake on the preceding 24-hour period. The method is adapted to gather additional information concerning the packaging, storage, and preparation of food by the participants. Trained dietitians will carry out the interviews during the clinic visits. The interviews will vary in length between 15 and 60 minutes depending on the stage of the study, and the complexity of each participants' diet. They will be carried out once during screening and three times during the 4-week intervention.

24-hour personal care product recall (24HR-PPR): This is a self-administered questionnaire for the 24-hour recall of personal care products use. This assessment will be conducted once during screening and three times during the 4-week intervention. The questionnaire consists of 15 questions and will take between 2 and 5 minutes to complete.

Post-trial survey: This survey will be conducted to identify any difficulties experienced by the participants that might have affected their adherence to the intervention and procedures.

Tolerability and feasibility qualitative interview: To evaluate the tolerability and feasibility of the trial intervention, participants will be invited to participate in a phone interview within two weeks of completing the intervention. A trained interviewer will conduct the interviews using a structured guide that includes both closed and open-ended questions. Each interview is expected to last 20-40 minutes.