Oxidation and fragmentation of plastics in a changing environment; from UV-radiation to biological degradation.

Understanding the fate of plastics in the environment is of critical importance for the quantitative assessment of the biological impacts of plastic waste. Specially, there is a need to analyze in more detail the reputed longevity of plastics in the context of plastic degradation through oxidation and fragmentation reactions. Photo-oxidation of plastic debris by solar UV radiation (UVR) makes material prone to subsequent fragmentation. The fragments generated following oxidation and subsequent exposure to mechanical stresses include secondary micro- or nanoparticles, an emerging class of pollutants. The paper discusses the UV-driven photo-oxidation process, identifying relevant knowledge gaps and uncertainties. Serious gaps in knowledge exist concerning the wavelength sensitivity and the dose-response of the photo-fragmentation process. Given the heterogeneity of natural UV irradiance varying from no exposure in sediments to full UV exposure of floating, beach litter or air-borne plastics, it is argued that the rates of UV-driven degradation/fragmentation will also vary dramatically between different locations and environmental niches. Biological phenomena such as biofouling will further modulate the exposure of plastics to UV radiation, while potentially also contributing to degradation and/or fragmentation of plastics independent of solar UVR. Reductions in solar UVR in many regions, consequent to the implementation of the Montreal Protocol and its Amendments for protecting stratospheric ozone, will have consequences for global UV-driven plastic degradation in a heterogeneous manner across different geographic and environmental zones. The interacting effects of global warming, stratospheric ozone and UV radiation are projected to increase UV irradiance at the surface in localized areas, mainly because of decreased cloud cover. Given the complexity and uncertainty of future environmental conditions, this currently precludes reliable quantitative predictions of plastic persistence on a global scale.

Neutral polyfluoroalkyl substances in the global atmosphere.

Concentrations of neutral per- and polyfluoroalkyl substances (nPFAS) in the atmosphere are of interest because nPFAS are highly mobile percursors for perfluoroalkyl acids. Two calibration studies in Ontario, Canada and Costa Rica established the feasibility of using XAD 2-resin based passive air samplers (XAD-PAS) to reliably determine long term average air concentrations of nPFAS under temperate and tropical climatic conditions. The temporal and spatial distribution of nPFAS was investigated by analyzing XAD-PAS deployed for one year at between 17 and 46 sites on six continents between 2006 and 2011 as part of the Global Atmospheric Passive Sampling (GAPS) study. Higher levels of fluorotelomer alcohols (FTOHs) compared to fluorinated sulfonamides (FOSAs), and fluorinated sulfonamidoethanols (FOSEs) were observed at all sites. Urban sites had the highest levels of nPFAS compared to rural and remote sites, which is also apparent in a positive correlation of nPFAS levels with the proximity of a sampling site to areas of high population density. Levels of FOSAs and FOSEs tended to decrease during the six years of measurements, whereas an initial decline in the concentrations of FTOHs from 2006 to 2008 did not continue in 2009 to 2011. A comparison of nPFAS levels measured in national XAD-PAS networks in Costa Rica and Botswana revealed that the GAPS sites in Tapanti and the Kalahari are representative of the more remote regions in those countries. XAD-PAS derived absolute nPFAS levels at GAPS sites are lower than those measured using another PAS, but are within the range of levels measured with active air samplers. Agreement of relative nPFAS composition is better between samplers, suggesting that the discrepancy is due to uncertain sampling rates.

Spatial and temporal trends of chiral organochlorine signatures in Great Lakes air using passive air samplers.

Passive air samples (PAS) were collected and analyzed to assess the spatial and temporal trends of chiral organochlorine signatures in the Laurentian Great Lakes. Samples were collected from 15 sites and analyzed for the concentrations and enantiomer signature of chlordanes and alpha-hexachlorocyclohexane (alpha-HCH). Levels of the chlordanes were typically 4 times higher in urban areas than what were observed at rural and remote locations, exhibiting strong urban-rural gradients. Near racemic residues were seen for the chlordane enantiomers in samples collected from sites located in Toronto and Chicago, which can be attributed to continued emissions of historical use of the technical chlordane mixture, while the chiral signature observed at sites located in rural and remote locations was indicative of an aged source. Knowledge of the spatial and temporal distribution of the enantiomer signatures of chlordane and alpha-HCH in air is useful for distinguishing sources of these compounds to ambient air. Results suggest that potential sources, such as those associated with Toronto and Chicago, have limited influence over the levels at rural and remote sites within the Great Lakes. Sources that are relatively close to sample sites, however, have a strong influence on levels observed at those sites. For instance, results indicate that Lake Superior continues to act as a source of alpha-HCH to sites located on its shores. Generally, it appears that during the warmer months, local enhanced surface-air exchange influences air concentrations and that during the cooler periods of the year, levels in the atmosphere are more strongly influenced by advective transport from source regions.

Concentrations of decabromodiphenyl ether in air from Southern Ontario: implications for particle-bound transport.

Atmospheric concentrations are reported for the main component of the brominated flame retardant decaBDE (BDE-209) in air samples collected from Southern Ontario for the period January 23-June 06, 2002. Levels ranged from below detection to 105pgm(-3) with virtually all of BDE-209 being trapped by the filter and thus deduced to be sorbed to aerosol particles. Thus, it is likely that the long-range atmospheric transport (LRAT) of BDE-209 is controlled by the transport characteristics of the aerosols. This conclusion that BDE-209 does not have the same potential for LRAT as other more volatile PBDEs is subject to possible complications arising from the uncertainties about the LRAT potential of aerosols.

Passive and active air samplers as complementary methods for investigating persistent organic pollutants in the Great Lakes Basin.

Data obtained using passive air samplers (PAS) are compared to active high-volume air sampling data in order to assess the feasibility of the PAS as a method, complementary to active high-volume air sampling (AAS), for monitoring levels of organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in the Laurentian Great Lakes. PAS were deployed at 15 of the Integrated Atmospheric Deposition Network (IADN) sites on a quarterly basis between July 2002 and June 2003, and PAS and AAS results are compared. Levels for the OC pesticides are typically highest in agricultural areas, with endosulfan I dominating air concentrations with values ranging between 40 and 1090 pg x m(-3), dieldrin values between 15 and 165 pg x m(-3), and gamma-HCH values between 13 and 100 pg x m(-3). alpha-HCH was seen to be relatively uniform across the Great Lakes Basin with values ranging between 15 and 73 pg x m(-3). Large urban centers, such as Chicago and Toronto, have the highest levels of PCBs and PBDEs that range between 400 and 1200 pg x m(-3) and 10 and 70 pg x m(-3), respectively. Comparison of the AAS and the PAS data collected during this study shows good agreement, within a factor of 2 or 3, suggesting that the two sample methods produce comparable results. It is suggested that PAS networks, while providing data that are different in nature from AAS, can provide a cost-effective and complementary approach for monitoring the spatial and temporal trends of persistent organic pollutants.

[Isotretinoin: compliance with recommendations in childbearing women]. / Isotrétinoïne: suivi de l'application des recommandations des prescriptions chez les femmes en âge de procréer.

INTRODUCTION: The aim of this survey is to ascertain if the incidence of isotretinoin exposed pregnancies was reduced by the late recommendations of prescription and issue (AMM modification on 06/08/2001 and 25/09/2001). METHODS: All isotretinoin exposed pregnancies registered by the French Regional Drug Monitoring Centres, the Information Centre for Teratogenic Agents and Roche (Roaccutane), Pierre Fabre (Curacné Gé) and Expanscience (Procuta Gé) laboratories, from January 1st, 1999 to December 31st, 2002, were analysed. Enforcement of the strengthening of isotretinoin prescription recommendations was analysed on a sample of 68 prescriptions from 45 pharmacies throughout France. RESULTS: In 4 years, 103 isotretinoin exposed pregnancies (Roaccutane 97 p. 100, Curacné(R) Gé 3 p. 100) during teratogenic risk period, were registered. Pregnancy started less than one month after isotretinoin stopping (37 p. 100), during the treatment (43 p. 100), or was in progress when the treatment was initiated (20 p. 100). The reason of the 22 lacking contraception was known 12 times, i.e. an absence of prescription (6 times), a refusal to take a prescribed contraception (3 times) and a self-medication (3 times). Among the 71 pregnancies whose contraceptive status is known, 48 p. 100 could had been avoided if recommendations had been followed (pregnancies due to a premature stopping or an absence of contraception). The issue of pregnancies is a voluntary termination in 60 cases (87 p. 100). Malformations frequency is 25 p. 100. Incidence of isotretinoin exposed pregnancies remained stable, 0.26/1000 treated women (vs 0.34 after 2001's AMM modifications). Of 68 prescriptions studied, 23 (24 p. 100) carried all the legal warnings, which is close to the previous survey's results. Contraception was in accordance with the recommendations in 78 p. 100 of cases and women learned and applied information given in 38 p. 100 of cases. At last, only 6 patients (9 p. 100) have both a correctly written prescription, a contraception and a time between the pregnancy test date and prescription and issue dates, in accordance with the licence and have had a correct information and understood it. Regarding the previous survey, pregnancy test before treatment was more often prescribed (96 p. 100 vs 88 p. 100). On the other hand, less women knew the necessity to keep on taking contraception one month after isotretinoin stopping (82 p. 100 vs 93 p. 100). CONCLUSION: Despite 3 successive isotretinoin prescription and issue recommendations strengthening in childbearing women, pregnancies can't be totally avoided. Bad compliance concerns the prescription and/or an incomplete or not understood information by the patient who does not scrupulously apply the care and contraception agreement. However, this study does not allow to assess the proportion of issued prescriptions despite their non-accordance with the licence criteria. The National Commission of Pharmacovigilance did not like to limit isotretinoin prescription to dermatologists only. It estimates that the administrative authority must intensify information by dermatologists, general practitioners and pharmacists, about measures to take to avoid an exposure to isotretinoin during pregnancy.

Evidence for the "grasshopper" effect and fractionation during long-range atmospheric transport of organic contaminants.

Although there is indisputable evidence that long-range atmospheric transport (LRAT) of organic contaminants occurs on a global scale, uncertainties remain about the detailed mechanism and extent of this phenomenon as well as the physical-chemical properties which facilitate LRAT. In this study, we discuss how mass balance models and monitoring data can contribute to a fuller understanding of the mechanism and extent of LRAT. Specifically we address the issues of "grasshopping" or "hopping" (the extent to which molecules are subject to multiple hops as distinct from a single emission-deposition event) and "global fractionation" (the differing behavior of chemicals as they are transported). It is shown that simple mass balance models can be used to assist the interpretation of monitoring data while also providing an instrument that can be used to assess the LRAT potential and the extent of hopping that organic substances may experience. The available evidence supports the notion that many persistent organic pollutants experience varying degrees of "hopping" during their environmental journey and as a consequence become fractionated with distance from source.

Modelling the environmental fate of the polybrominated diphenyl ethers.

In response to growing alarm over the occurrence of polybrominated diphenyl ethers (PBDEs) in remote regions, this study considers their physical chemistry, environmental partitioning and considerations regarding potential for long-range atmospheric transport (LRAT). Internally consistent physical-chemical property data are presented for five representative congeners (PBDE-15, -28, -47, -99, -153) and used in a multimedia modelling approach. Results of the Level II model indicate that PBDEs will largely partition to organic carbon in soil and sediment and that their persistence will be strongly influenced by degradation rates in these media that are not well known. TaPL3 model estimates of their characteristic travel distance (CTD) suggest limited LRAT potential. The LRAT is also evaluated qualitatively, in terms of surface-air exchange behaviour. PBDEs are shown to be sensitive to seasonally and diurnally fluctuating temperatures. When vegetation is included in the model, 50% of the total mass of PBDE-47 deposited to vegetation returns to the atmosphere, suggesting that it may migrate through a series of deposition/volatilisation hops. Key data that needs to be identified in this evaluation include a better understanding of air-surface exchange, particularly to foliage, and measurements of degradation rates in soil, sediment and vegetation.

Air-surface exchange of polybrominated diphenyl ethers and polychlorinated biphenyls.

Air and leaf-litter samples were collected from a rural site in southern Ontario under meteorologically stable conditions in the early spring, prior to bud burst, over a three-day period to measure the simultaneous diurnal variations in polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). PBDEs are used in a wide range of commercial products as flame retardants and are being assessed internationally as potential persistent organic pollutants. Total PBDE concentrations in the air ranged between 88 and 1250 pg m(-3), and were dominated primarily by the lighter congeners PBDEs 17, 28, and 47, and concentrations of total PCBs ranged between 96 and 950 pg m(-3), and were dominated by the lower chlorinated (tri- to tetra-) congeners. Slopes of Clausius-Clapeyron plots indicate that both PCBs and PBDEs are experiencing active air-surface exchange. Fugacities were estimated from concentrations in the air and leaf-litter and suggest near equilibrium conditions. Following the three-day intensive sampling period, 40 air samples were collected at 24-hour intervals in an attempt to evaluate the effect of bud burst on atmospheric concentrations. Total PBDE concentrations in the daily air samples ranged between 10 and 230 pg m(-3), and were dominated by the lighter congeners PBDE 17, 28, and 47, whereas concentrations of total PCBs ranged between 30 and 450 pg m(-3) during this period. It is hypothesized thatthe high PBDE concentrations observed at the beginning of the sampling period are the result of an "early spring pulse" in which PBDEs deposited in the snowpack over the winter are released with snowmelt, resulting in elevated concentrations in the surface and air. Later in the sampling period, following bud burst, PBDE concentrations in air fell to 10 to 20 pg m(-3), possibly due to the high sorption capacity of this freshly emerging foliage compartment.