Abstract Over 9000 people die of Melanoma in the United States every year [1]. It is the most common skin cancer. DNA damage from UV light can be measured in all skin types and all skin types may develop melanoma from DNA damage [3]. While chemical sunscreens have made progress toward removing aesthetic concerns, these chemicals can enter the bloodstream with uncertain health effects. Physical sunscreens based on ZnO/TiO2 do not have the same risk, however the white/”ashy” appearance on darker skin limits their adoption. This proposal is for the development of a physical sunscreen based on the non-toxic, biocompatible, and naturally occurring polyester poly-3-hydroxybutyrate (PHB) that is by nature less whitening than physical sunscreens on the market, allowing for greater adoption by individuals with darker skin. PHB is part of the natural carbon cycle and readily biodegrades in marine environments. Light transmission through PHB’s crystal structure increases with increasing wavelength; PHB blocks up to much more UV light than visible light, giving it a less white appearance than minerals that reflect visible light. The specific aims of this proposal are to: 1) Produce and isolate PHB for sunscreen formulation; 2) Obtain a range of particle and crystal spherulite sizes by varying spray drying/annealing parameters; and 3) to study the effects of particle size and spherulite size on UV light transmission and sensory acceptance (specifically grittiness). It is important to design sunscreen products that address the tone issues while limiting uncertain health/environmental risks. Making sunscreen that is inclusive of all skin tones will help increase application to all ethnicities equally and will help lessen the health gap by reducing the mortality rate of people who develop melanoma. Our innovation will address these issues and is superior to other sunscreens. Our innovative sunscreen is designed to be (1) bio-based and biodegradable making it (2) a safe and healthy option, (3) that doesn’t have a perceivable tone and (4) has removes the negative environmental impact that is associated with many sunscreens on the market today.