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4 Fate, Transport, and Potential Exposure in the Environment
Pages 69-102

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From page 69...
... Recognizing the need to consider the physical features of environments that influence exposures, and that those features vary across systems, the third section provides an overview of the range of hydrological conditions that influence the fate and transport of introduced UV filters. The fourth section reviews the data on environmental exposures with respect to measured concentrations in water and sediment, and links this back to environmental settings and the fate characteristics of the UV filters.
From page 70...
... The importance of these properties are well recognized in the conduct of environmental risk assessments and explains why they are generally required prior to conducting risk assessments. FATE CHARACTERISTICS OF UV FILTERS The physico-chemical properties of chemicals largely drive environmental behavior (i.e., fate and effects)
From page 71...
... Dubelcco's media contained 34 mg/L zinc compared to nanopure water which had 7.40 mg/L, and suggests that in biological FIGURE 4.1  Inorganic UV filter fate processes in surface waters. SOURCE: Adapted from Suhendra et al., 2020.
From page 72...
... The lifetime of inorganic UV filters in the water column is determined by their size, density, surface charge, and tendency to aggregate with other particles in water, which then promotes settling to sediments. Physico-Chemical Parameters of Organic UV Filters Impacting Fate The physico-chemical properties of the organic UV filters necessary for conducting environmental risk assessments include solubility, volatility, acid dissociation constants (if appropriate)
From page 73...
... (Log Kow)
From page 74...
... (Log Kow)
From page 75...
... is the fact that for ionogenic organic chemicals -- chemicals that can exist as ions in solution -- the solubility can be impacted by the charge state of the chemical, which is in turn dependent on parameters such as the acid-dissociation constant(s) for the chemicals (i.e., pKa values)
From page 76...
... For ionogenic organic chemicals, which often have high solubilities and low vapor pressures (only the neutral form is expected to volatilize) , the pH of the aqueous system also complicates Henry's Law constants.
From page 77...
... , which quantitatively relates the amount of a chemical found on solids to that dissolved in the water phase. For many organic chemicals and environmental solids, the Kd value can be normalized to the fraction of the solid phase composed of organic carbon (foc; as this is the primary sorbent in environmental scenarios)
From page 78...
... . Organic chemicals -- including organic UV filters -- have the potential to partition into the SML (Guitart et al., 2004)
From page 79...
... Metabolites formed in both Benzophenone-1a Fungus, Trametes Sewage sludge at 10 ~98% degradation of parent, high Badia-Fabregat et al., versicolor mg/L laccase activity; 4HB and 4DHB 2012a (metabolites) were slowly eliminated Benzophenone-1a Staphylococcus aureus Seeded on solid phase 2.5–26.7% removal; 1–24% removal Chiriac et al., 2021 and Enterococcus faecalis nutrient medium of the metabolite 4HB dosed alone (gram +)
From page 80...
... 80 IMPLICATIONS OF SUNSCREEN USAGE FOR AQUATIC ENVIRONMENTS AND HUMAN HEALTH for higher removal from wastewater. Oxybenzone metabolites were more metabolized by Trametes versicolor (Badia-Fabregat et al., 2012a)
From page 81...
... present in the water column. In many cases, phototransformation can be described as photodegradation, where the concentration of the parent chemical declines.
From page 82...
... is important for determining their transport, fate, and potential exposure to aquatic organisms. In general, due to the wide range of aquatic habitats that UV filters may enter via recreational activities, and the varied inputs discussed in Chapter 3, assessing risk will require inclusion of the unique dynamics of the water bodies considered.
From page 83...
... , some values may be biased by the addition of organic additives to enhance UV filter solubility. ESTIMATED AND MEASURED CONCENTRATIONS IN WATER AND SEDIMENTS Exposure assessments for chemicals in aquatic environments typically include estimates or measures of chemical concentrations in water, sediments, and/or internally in biota (i.e., tissue residue levels)
From page 84...
... Estimating UV Filter Concentrations Concentrations of UV filters in the aquatic environment vary due to numerous and diverse sources, dilution, and environmental fate processes. Each of these factors affects the levels of UV filters to which an organism might be exposed, with the duration of exposure also critical in determining effect.
From page 85...
... While passive samplers deployed in surface waters may provide an indication of average exposure levels, they would likely not be able to characterize the short-term variations or pulses in exposure levels in the water. For sediments, temporal variations in UV filter concentrations are likely dampened relative to water concentrations, and passive samplers could provide a longer-term measure of exposure of organisms living on or within the sediments; an example is the evaluation carried out by Muz et al.
From page 86...
... . Although predicted estimates are typically above concentrations of UV filters measured in surface waters, modeled and measured aquatic and sediment concentration data provide potential ranges, including upper bounds, and probabilities of exposure levels of UV filters to organisms.
From page 87...
... Temporal and spatial variations in UV filter concentrations at a sampling location can vary over orders of magnitude depending on the factors explored in this chapter and this will be a critical factor for assessing exposures. The compilation of values gives insight into spatial and temporal variability, reflects the differential fate characteristics of the UV filters, and reflects patterns of sunscreen usage.
From page 88...
... The highest reported values for beaches are from beaches at embayments, in shallower water, where water residence times are likely greater than for more open coastlines, and where there is higher use by people (hence higher input to water volume and flushing location)
From page 89...
... . Because of the analytical challenges that can arise in the analysis of UV filters (see section on Analytical Chemistry Considerations)
From page 90...
... . The outcome of this qualitative examination suggests that source strength, proximity to source, and residence time converge to varying degrees from place to place to yield higher or lower concentrations of oxybenzone in water.
From page 91...
... FATE, TRANSPORT, AND POTENTIAL EXPOSURE IN THE ENVIRONMENT 91 FIGURE 4.6  Oxybenzone concentrations are arranged as four bins from high to low (left to right) in relation to the combined influences of source strength, proximity to source, and water residence time.
From page 92...
... Additionally, it may be possible to make total estimates by extrapolating from the current data set with respect to individual UV filter concentrations relative to totals. In addition to the committee's analysis, individual studies show variation in UV filter concentrations across spatial as well as temporal scales.
From page 93...
... (2019) investigated the relative concentrations of UV filters including oxybenzone and avobenzone in the SML and surface water of the main beach in Banyuls-sur-Mer and a nearby artificial lake in Villeneuve-de-la-Raho; the authors note that these two water bodies in France receive highly increased tourism pressure during the summer months.
From page 94...
... . The fate properties described for the UV filters earlier in this chapter provide insight into UV filter specific characteristics that will govern their distribution in the water column and sediments.
From page 95...
... Inorganic UV Filters in Water and Sediments Including the Sea Surface Microlayer (SML) In comparison to organic UV filters for which there are observations about concentrations in surface waters, data are limited on the incremental influence of inorganic UV filters on concentrations of titanium and zinc in the environment.
From page 96...
... A main factor influencing the lack of reported data on ZnO and TiO2 inorganic UV filter concentrations is the analytical difficulty in distinguishing sunscreen formulation and uses of ZnO and TiO2 from other anthropogenic uses of these materials or natural sources of these metals and minerals. Past attempts to fingerprint TiO2 sources and attribute sunscreens as a source of TiO2 in bathing areas used trace elements present with titanium.
From page 97...
... How and when these samples are collected during the test is important to ensure accurate representation of test exposures, especially when toxicity test designs do not use a continuous flow-through exposure regime but rather a static-renew design whereby exposure solutions are made and replaced over the course of the experiment, typically daily (see Chapter 6)
From page 98...
... Electron microscopy imaging with elemental analysis techniques can be applied to characterize the size, shape, and composition of UV filters. The most significant analytical challenge regarding inorganic UV filters is the lack of a robust analytical protocol to differentiate inorganic UV filters from other sources of similar minerals/elements, and lack of high throughput analytical methods to image (e.g., electron microscopy)
From page 99...
... FIGURE 4.12  Summary of analytical methods for inorganic UV filters across their life cycle from manufacturing through use and into the environment.
From page 100...
... Modeled estimates are typically designed to provide ranges, including upper estimates, of possible exposures based on estimates of loadings to the environment combined with fate characteristics (including adsorption and treatment within wastewater treatment systems for down-the-drain sources) and environmental fate and transport processes in the receiving water environment.
From page 101...
... . Given the potential for particle-bound exposures for filter feeding aquatic organisms, such data could be considered critical for risk assessments.
From page 102...
... This may include minimum replicates and reliable, standardized methods developed to collect, extract, and process samples so that they accurately measure UV filters from environmental samples. This would also include minimum QA/QC procedures (e.g., analytical and matric recovery spikes)


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