The Effects of Sunscreen Chemicals on Chicken Embryological Development

Overview

We studied the potential teratogenic effects of popular chemical sunscreens. Teratogens are substances that can harm the development of a fetus. The embryos of the common chicken Gallus gallus domesticus were used as a model system because of their short incubation period and well-characterized embryologic development. With an incubation period of ~22 days, this allows for short experiments of less than a week. Embryos were incubated in their eggs for ~2 days before being transferred to sterile nutrient media in petri dishes. Two substances were tested: Coppertone SPORT Continuous Sunscreen Spray Broad Spectrum SPF 50 and Banana Boat Ultra Sport Sunscreen Spray SPF 50+; both were diluted to a 0.0001% solution with sterile isotonic saline and compared to a control of sterile isotonic saline. Two methods of sunscreen exposure were used: in vivo (in an egg) and in vitro (in a petri dish). In vivo exposure was accomplished by drilling a hole in the eggshell and injecting either the test or control solutions either into the air sac or directly into the albumen of the egg. The in vivo exposure groups were injected immediately before initial incubation. Two days later, all embryos were removed from their eggs and placed on agar. For the in vitro groups, sunscreen dilutions or control saline were pipetted onto embryos that had been transferred to sterile media in petri dishes. All embryos of both in vivo and in vitro groups were photographed with an SMZ-U Nikon stereo zoom light microscope at 75x mag. during the same time slots for the next four days. Embryos were monitored for lifespan, peak length, and peak 2D area determined from photo analysis in Image J. We hypothesized that embryos exposed to sunscreen would have shorter lifespans, shorter peak lengths, and smaller 2D areas than embryos not exposed to sunscreen. All embryos were euthanized on day 4. Embryos exposed in vivo to Coppertone reached a peak 2D area 53% as large as embryos exposed to the control saline in vivo, and embryos exposed to Banana Boat in vivo reached a peak 2D area 48% larger than control embryos. Controls subjected to either method of exposure lived ~0.1 to 1.3 days longer, on average, than embryos exposed to a chemical sunscreen. This suggests that Banana Boat and Coppertone spray sunscreens may be harmful to chicken embryos in their early stages of development, however further investigation is needed to elucidate their effects.

Competition history

• AJAS 2020 Category not listed

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