As surface ultraviolet-B (UV-B) radiation levels increase due to the decline in the protective stratospheric ozone layer, ultraviolet radiation sunscreens will become more important for all plant species that grow in sunlight. Epicuticular waxes, which cover the aerial portions of all terrestrial plants, are ideally located to be sunscreens. The sun-screening ability of maize (Zea mays L.) epicuticular waxes was tested using the glossy1 mutant, which is specifically defective in juvenile wax production. A significant difference between the glossy1 mutant and wild type was seen in UV-induced leaf rolling and in some measurements of UV-induced DNA damage levels under enhanced UV. Isolated epicuticular wax layers absorbed significant amounts of UV, and leaves with wax absorbed more UV than leaves with little wax. Thus, by some measures, the epicuticular waxy layer acts as an ultraviolet radiation protectant in maize.

Pharmaceutically active compounds (PhACs) are released into the environment where they undergo soil sorption, photodegradation, and chemical transformation into structurally similar compounds. Here we report on studies of naproxen (NAP) and ibuprofen (IBP), two widely-used nonsteroidal anti-inflammatory drugs (NSAIDS), in soils and water. Organic matter (OM) was observed to play an important role in each of these processes. Sorption was observed to be stronger and nonlinear in higher OM soils while weaker but still significant in lower OM, higher clay soils; the amphiphilic nature of these two PhACs combined with the complex charged and nonpolar surfaces available in the soil was observed to control the sorption behavior. Simulated solar photodegradation rates of NAP and IBP in water were observed to change in the presence of humic acid or fulvic acid. Structural analogs of each compound were observed as the result of chemical transformation in both photoexposed aqueous solutions and non-photoexposed soil. Two of these transformation products were detected as both soil and photo transformation products for both PhACs. OM was observed to influence the chemical transformation of both pharmaceuticals.

The forced degradation of 11 ibuprofen tablet brands was carried out according to current industry best practices. The results indicated an incompatibility between ibuprofen and two common tablet excipients (polyethylene glycol and polysorbate 80) that were observed to accelerate the degradation of ibuprofen in tablets stored for three weeks at 70°C/75% RH. Studies of binary drug/excipient samples supported the conclusion. One degradant that was observed at increased levels was 4-isobutylacetophenone (4-IBAP), which is a known toxin.

Although pharmaceutical pollution is a global environmental concern, much remains unknown about the transformation of pharmaceuticals in the wild and their effects on wildlife. In the environment, pharmaceuticals typically transform to some extent into different, structurally related compounds. Pharmaceutical transformation products resulting from exposure to sunlight (i.e., ultraviolet radiation) in surface waters are of particular concern; these products can be more hydrophobic, persistent, and toxic than their parent compounds. In the present study, naproxen, a widely used nonsteroidal anti‐inflammatory drug, and its phototransformation products were studied to assess the overall persistence and photochemical fate of naproxen. Southern toad (Anaxyrus terrestris) larvae were used as model aquatic vertebrates to evaluate the acute toxicity of naproxen and its phototransformation products singly and in mixtures. The phototransformation products were observed to be more persistent and more toxic than naproxen itself. The slower phototransformation of the phototransformation products relative to naproxen suggests a greater potential to accumulate in the environment, particularly when naproxen is continually released. Mixtures of naproxen and its phototransformation products, in ratios observed during phototransformation, were more toxic than naproxen alone, as predicted by the model of concentration addition and the greater toxicity of the phototransformation products. Together, these results indicate that the ecological risk of naproxen may be underestimated by considering environmental levels of naproxen alone. Environ Toxicol Chem 2019;38:2008–2019. © 2019 SETAC.