Olivier Thomas | EHESP (Ecole des hautes études en santé publique) (original) (raw)

Papers by Olivier Thomas

Journal of Environment Quality, 2015

ABSTRACT There is emerging concern over the impact of extreme events such as heavy rainfall on th... more ABSTRACT There is emerging concern over the impact of extreme events such as heavy rainfall on the quality of water entering the drinking water supply from aboveground sources, as such events are expected to increase in magnitude and frequency in response to climate change. We compared the impact of rainfall events on streamwater quality in four contrasting upland (peatland and mineral soil) and lowland agricultural catchments used to supply drinking water in France (Brittany) and the United Kingdom (North Wales) by analyzing water samples collected before, during, and after specific events. At all four streams, heavy rainfall led to a considerable rise in organic matter concentration ranging from 48 to 158%. Dissolved organic carbon (DOC) quality, as determined using specific ultraviolet absorbance, changed consistently at all sites during rainfall events, with a greater proportion of aromatic and higher molecular weight compounds following the onset of rainfall. However, the change in DOC quality and quantity did not significantly alter the trihalomethane formation potential. We observed small increases in trihalomethane (THM) generation only at the Welsh peatland and agricultural sites and a small decrease at the Brittany agricultural site. The proportion of brominated THMs in chlorinated waters was positively correlated with bromide/DOC ratio in raw waters for all sites and hydrological conditions. These results provide a first indication of the potential implications for surface-based drinking water resources resulting from expected future increases in rainfall event intensity and extension of dry periods with climate changes.

Water Research, 2014

Anti-cancer drugs are an important class of pharmaceutical products. Methotrexate (MTX) is a foli... more Anti-cancer drugs are an important class of pharmaceutical products. Methotrexate (MTX) is a folic acid antagonist used in high doses as antimetabolite in anti-cancer treatment as well as in low doses for the treatment of rheumatoid arthritis and adults' psoriasis. In the past, several anti-cancer drugs, including methotrexate, have been found in the environment. Their presence in water, especially if used for the production of drinking water, is even in low concentrations of particular interest, due to the risk to retrieve them in the consumed water and their high activity and grave effects. But prior to usage as drinking water, raw waters are treated and chlorination is a common practice in several countries. As such a treatment can lead to the formation of organochlorine in water, the study of the fate of MTX during chlorination in a batch trial was carried out. The reaction was monitored by dissolved organic carbon (DOC) and by fluorescence and UV spectroscopy. Investigation of by-products formed was done with liquid chromatography/mass spectrometry (LC/MS). Under the given experimental conditions, Methotrexate was eliminated rapidly (t1/2 around 21 min). However, DOC elimination was incomplete. Monitoring with LC-MS showed the formation of a monochlorinated transformation product of MTX. In silico analysis of the proposed transformation products for different carcinogenic, mutagenic and genotoxic endpoints with different software platforms provided no clear evidence that the possible transformation products after chlorination might be more toxic than the parent compound. However, since a number of alerts is altered after chlorination, it cannot be excluded that the toxicity of these transformation products might be modulated compared with the parent compound.

Acta hydrochimica et hydrobiologica, 1998

Industrial wastewater management is nowadays a reality in most industries and particularly in pet... more Industrial wastewater management is nowadays a reality in most industries and particularly in petrochemical ones. As a consequence, some treatment plants appear to be over designed because of waste minimization. Actually supplementary organic loads coming from incidents or external effluents have to be treated. As classical parameters or compound analyses are not well adapted, a new methodology based on the

ABSTRACT In 3D integration, interconnections between stacked dies are ensured by conductive throu... more ABSTRACT In 3D integration, interconnections between stacked dies are ensured by conductive through silicon vias. Electrical conduction is achieved via coating the vias sidewalls with a metal, such as tungsten. In this work we have compared thermal-dependent stress of thin tungsten films deposited either in full plate oron vias sidewalls. The comparison of stress measurements at room temperature and during heating cycles reveals large differences between full plate and vias samples. At room temperature, in the vias samples, the stress is a factor 4 less than it is in the full plate sample, with both values indicating a tensile stress. While a thermo-elastic behavior is expected for the full plate sample, no stress evolution as a function of temperature is observed in the case of the vias samples.

Heavy rainfall events, increasing in frequency and intensity with climate change, impact on the q... more Heavy rainfall events, increasing in frequency and intensity with climate change, impact on the quality of the water resource used for drinking-water production. Small-scale water suppliers are particularly sensitive because of their management and the related difficulties of adapting treatment to variations. Decision-support systems, based on monitoring and analytical tools, need to be developed to improve crisis-management procedures related to

The composition of water and wastewater, varying temporally and spatially, depends on factors suc... more The composition of water and wastewater, varying temporally and spatially, depends on factors such as environmental context, types of pollution sources, weather conditions leading to dilution or solids transportation, length of sewer network, etc. Because quantitative parameters are often not adapted for the characterization of wastewater quality variability, a nonparametric measurement is proposed, based on comparison of the UV absorption spectra of samples. The presence of isosbestic points, occurring in the set of spectra either directly or indirectly after normalization, allows quantification of the variability of a given water or effluent. A normalization step is used when dilution exists in the case of a mixture of water types (discharge or rain). Several examples show how to calculate the variability or to estimate the dilution factor from UV spectra data, even without results of physicochemical parameters.

Chromium(VI) is one of the major pollutants of waters and unfortunately, at the present time, it ... more Chromium(VI) is one of the major pollutants of waters and unfortunately, at the present time, it cannot be determined with a simple and fast method. The use of the ultraviolet multiwavelength absorptiometry (UVMA) for chromium determination is very convenient for that purpose because of the well known absorption properties of chromium. Two methods are proposed which lead to different sensitivity. The first one needs hydroxide sodium addition for the measurement of the chromate form and has a detection limit of 4 gg/1. The second does not use any reagent and determines directly both dichromate and chromate forms, whose sum gives the concentration of chromium(VI). This last procedure is faster but the characteristics are slightly less precise. These proposed methods have been compared with a reference method, for natural waters and treated wastewaters, with good agreement. These procedures can be used for water quality monitoring.

Talanta, 1999

Total organic carbon (TOC) is one of the most important parameter for the knowledge of water and ... more Total organic carbon (TOC) is one of the most important parameter for the knowledge of water and wastewater quality, because it concerns theoretically all organic compounds. Unfortunately, some restrictions with respect to TOC measurement must be considered, explaining that alternative procedures have been envisaged, among which UV spectrophotometry. Starting from a comparison of results between high temperature digestion and UV photo-oxidation techniques for some specific compounds and real wastewater samples, the work shows the complementary interest of using UV spectrophotometry either directly (with multiwavelength procedures) or after UV photo-oxidation.

The occurrence of cyanobacterial blooms is drastically increasing in temperate countries and drin... more The occurrence of cyanobacterial blooms is drastically increasing in temperate countries and drinking water resources are threatened. As a result, cyanotoxins should be considered in water treatment to protect human health. This study presents a state of the art on cyanotoxins in water and their behaviour towards chlorination, a common drinking water disinfection process. Chlorination efficiency on cyanotoxins alteration depends on pH, chlorine dose and oxidant nature. Microcystins and cylindrospermopsin are efficiently transformed by chlorine, with respectively 6 and 2 by-products identified. In addition, chlorination of microcystins and cylindrospermopsin is associated with a loss of acute toxicity. Even though they have been less investigated, saxitoxins and nodularins are also altered by chlorine. For these toxins, no by-products have been identified, but the chlorinated mixture does not show acute toxicity. On the contrary, the fact that anatoxin-a has a very slow reaction kinetics suggests that this toxin resists chlorination.

In temperate countries, the occurrence of cyanobacterial blooms threatens drinking water resource... more In temperate countries, the occurrence of cyanobacterial blooms threatens drinking water resources. Consequently, cyanotoxins are increasingly considered in water treatment, and their reactions with chlorine used to disinfect drinking water are particularly investigated. This study presents new elements for further understanding of cylindrospermopsin chlorination, through reactants and by-products monitoring, UV spectrum examination, and cytotoxicity assessment on human intestinal Caco-2 cells. On the one hand, the evolution of mixture UV spectrum indicated that cylindrospermopsin was quickly transformed at least into one intermediate by-product. While mass spectrometry experiments confirmed that cylindrospermopsin was almost totally transformed within 5 min, chlorine was consumed up to 20 min after the beginning of the reaction with a rate of 5 mol per mol of toxin. Then, LC-MS analysis gave rise to the formation of a third cylindrospermopsin by-product in addition to 5-chloro-cylindrospermopsin and cylindrospermopsic acid previously identified. Thanks to the accurate mass measurement provided by the LTQ-Orbitrap mass spectrometer, this new and stable chlorination by-product was assigned the chemical formula C(13)H(18)N(4)O(7)S. On the other hand, both of the mitochondrial and lysosomal activities measured on Caco-2 cells revealed that cylindrospermopsin chlorination significantly decreases mixture cytotoxicity.

RSC Advances, 2012

The full chemical reinvestigation of the Mediterranean marine sponge Crambe crambe led to the iso... more The full chemical reinvestigation of the Mediterranean marine sponge Crambe crambe led to the isolation and structural characterization of 11 crambescin derivatives, including 8 new compounds, together with the known crambescidin 816. HRMS/MS studies allowed the complete assignment of the alkyl chain lengths of these guanidine alkaloids while the absolute configurations of all compounds were inferred from the comparison between experimental and theoretical circular dichroism spectra. Crambescidin 816 was proven to be more cytotoxic against neuronal cell lines than crambescin C1. ; Tel: +33 493377708 { Electronic supplementary information (ESI) available: NMR and HRMS spectra are given for compounds 1-11. See

Journal of Environment Quality, 2015

ABSTRACT There is emerging concern over the impact of extreme events such as heavy rainfall on th... more ABSTRACT There is emerging concern over the impact of extreme events such as heavy rainfall on the quality of water entering the drinking water supply from aboveground sources, as such events are expected to increase in magnitude and frequency in response to climate change. We compared the impact of rainfall events on streamwater quality in four contrasting upland (peatland and mineral soil) and lowland agricultural catchments used to supply drinking water in France (Brittany) and the United Kingdom (North Wales) by analyzing water samples collected before, during, and after specific events. At all four streams, heavy rainfall led to a considerable rise in organic matter concentration ranging from 48 to 158%. Dissolved organic carbon (DOC) quality, as determined using specific ultraviolet absorbance, changed consistently at all sites during rainfall events, with a greater proportion of aromatic and higher molecular weight compounds following the onset of rainfall. However, the change in DOC quality and quantity did not significantly alter the trihalomethane formation potential. We observed small increases in trihalomethane (THM) generation only at the Welsh peatland and agricultural sites and a small decrease at the Brittany agricultural site. The proportion of brominated THMs in chlorinated waters was positively correlated with bromide/DOC ratio in raw waters for all sites and hydrological conditions. These results provide a first indication of the potential implications for surface-based drinking water resources resulting from expected future increases in rainfall event intensity and extension of dry periods with climate changes.

Water Research, 2014

Anti-cancer drugs are an important class of pharmaceutical products. Methotrexate (MTX) is a foli... more Anti-cancer drugs are an important class of pharmaceutical products. Methotrexate (MTX) is a folic acid antagonist used in high doses as antimetabolite in anti-cancer treatment as well as in low doses for the treatment of rheumatoid arthritis and adults' psoriasis. In the past, several anti-cancer drugs, including methotrexate, have been found in the environment. Their presence in water, especially if used for the production of drinking water, is even in low concentrations of particular interest, due to the risk to retrieve them in the consumed water and their high activity and grave effects. But prior to usage as drinking water, raw waters are treated and chlorination is a common practice in several countries. As such a treatment can lead to the formation of organochlorine in water, the study of the fate of MTX during chlorination in a batch trial was carried out. The reaction was monitored by dissolved organic carbon (DOC) and by fluorescence and UV spectroscopy. Investigation of by-products formed was done with liquid chromatography/mass spectrometry (LC/MS). Under the given experimental conditions, Methotrexate was eliminated rapidly (t1/2 around 21 min). However, DOC elimination was incomplete. Monitoring with LC-MS showed the formation of a monochlorinated transformation product of MTX. In silico analysis of the proposed transformation products for different carcinogenic, mutagenic and genotoxic endpoints with different software platforms provided no clear evidence that the possible transformation products after chlorination might be more toxic than the parent compound. However, since a number of alerts is altered after chlorination, it cannot be excluded that the toxicity of these transformation products might be modulated compared with the parent compound.

Acta hydrochimica et hydrobiologica, 1998

Industrial wastewater management is nowadays a reality in most industries and particularly in pet... more Industrial wastewater management is nowadays a reality in most industries and particularly in petrochemical ones. As a consequence, some treatment plants appear to be over designed because of waste minimization. Actually supplementary organic loads coming from incidents or external effluents have to be treated. As classical parameters or compound analyses are not well adapted, a new methodology based on the

ABSTRACT In 3D integration, interconnections between stacked dies are ensured by conductive throu... more ABSTRACT In 3D integration, interconnections between stacked dies are ensured by conductive through silicon vias. Electrical conduction is achieved via coating the vias sidewalls with a metal, such as tungsten. In this work we have compared thermal-dependent stress of thin tungsten films deposited either in full plate oron vias sidewalls. The comparison of stress measurements at room temperature and during heating cycles reveals large differences between full plate and vias samples. At room temperature, in the vias samples, the stress is a factor 4 less than it is in the full plate sample, with both values indicating a tensile stress. While a thermo-elastic behavior is expected for the full plate sample, no stress evolution as a function of temperature is observed in the case of the vias samples.

Heavy rainfall events, increasing in frequency and intensity with climate change, impact on the q... more Heavy rainfall events, increasing in frequency and intensity with climate change, impact on the quality of the water resource used for drinking-water production. Small-scale water suppliers are particularly sensitive because of their management and the related difficulties of adapting treatment to variations. Decision-support systems, based on monitoring and analytical tools, need to be developed to improve crisis-management procedures related to

The composition of water and wastewater, varying temporally and spatially, depends on factors suc... more The composition of water and wastewater, varying temporally and spatially, depends on factors such as environmental context, types of pollution sources, weather conditions leading to dilution or solids transportation, length of sewer network, etc. Because quantitative parameters are often not adapted for the characterization of wastewater quality variability, a nonparametric measurement is proposed, based on comparison of the UV absorption spectra of samples. The presence of isosbestic points, occurring in the set of spectra either directly or indirectly after normalization, allows quantification of the variability of a given water or effluent. A normalization step is used when dilution exists in the case of a mixture of water types (discharge or rain). Several examples show how to calculate the variability or to estimate the dilution factor from UV spectra data, even without results of physicochemical parameters.

Chromium(VI) is one of the major pollutants of waters and unfortunately, at the present time, it ... more Chromium(VI) is one of the major pollutants of waters and unfortunately, at the present time, it cannot be determined with a simple and fast method. The use of the ultraviolet multiwavelength absorptiometry (UVMA) for chromium determination is very convenient for that purpose because of the well known absorption properties of chromium. Two methods are proposed which lead to different sensitivity. The first one needs hydroxide sodium addition for the measurement of the chromate form and has a detection limit of 4 gg/1. The second does not use any reagent and determines directly both dichromate and chromate forms, whose sum gives the concentration of chromium(VI). This last procedure is faster but the characteristics are slightly less precise. These proposed methods have been compared with a reference method, for natural waters and treated wastewaters, with good agreement. These procedures can be used for water quality monitoring.

Talanta, 1999

Total organic carbon (TOC) is one of the most important parameter for the knowledge of water and ... more Total organic carbon (TOC) is one of the most important parameter for the knowledge of water and wastewater quality, because it concerns theoretically all organic compounds. Unfortunately, some restrictions with respect to TOC measurement must be considered, explaining that alternative procedures have been envisaged, among which UV spectrophotometry. Starting from a comparison of results between high temperature digestion and UV photo-oxidation techniques for some specific compounds and real wastewater samples, the work shows the complementary interest of using UV spectrophotometry either directly (with multiwavelength procedures) or after UV photo-oxidation.

The occurrence of cyanobacterial blooms is drastically increasing in temperate countries and drin... more The occurrence of cyanobacterial blooms is drastically increasing in temperate countries and drinking water resources are threatened. As a result, cyanotoxins should be considered in water treatment to protect human health. This study presents a state of the art on cyanotoxins in water and their behaviour towards chlorination, a common drinking water disinfection process. Chlorination efficiency on cyanotoxins alteration depends on pH, chlorine dose and oxidant nature. Microcystins and cylindrospermopsin are efficiently transformed by chlorine, with respectively 6 and 2 by-products identified. In addition, chlorination of microcystins and cylindrospermopsin is associated with a loss of acute toxicity. Even though they have been less investigated, saxitoxins and nodularins are also altered by chlorine. For these toxins, no by-products have been identified, but the chlorinated mixture does not show acute toxicity. On the contrary, the fact that anatoxin-a has a very slow reaction kinetics suggests that this toxin resists chlorination.

In temperate countries, the occurrence of cyanobacterial blooms threatens drinking water resource... more In temperate countries, the occurrence of cyanobacterial blooms threatens drinking water resources. Consequently, cyanotoxins are increasingly considered in water treatment, and their reactions with chlorine used to disinfect drinking water are particularly investigated. This study presents new elements for further understanding of cylindrospermopsin chlorination, through reactants and by-products monitoring, UV spectrum examination, and cytotoxicity assessment on human intestinal Caco-2 cells. On the one hand, the evolution of mixture UV spectrum indicated that cylindrospermopsin was quickly transformed at least into one intermediate by-product. While mass spectrometry experiments confirmed that cylindrospermopsin was almost totally transformed within 5 min, chlorine was consumed up to 20 min after the beginning of the reaction with a rate of 5 mol per mol of toxin. Then, LC-MS analysis gave rise to the formation of a third cylindrospermopsin by-product in addition to 5-chloro-cylindrospermopsin and cylindrospermopsic acid previously identified. Thanks to the accurate mass measurement provided by the LTQ-Orbitrap mass spectrometer, this new and stable chlorination by-product was assigned the chemical formula C(13)H(18)N(4)O(7)S. On the other hand, both of the mitochondrial and lysosomal activities measured on Caco-2 cells revealed that cylindrospermopsin chlorination significantly decreases mixture cytotoxicity.

RSC Advances, 2012

The full chemical reinvestigation of the Mediterranean marine sponge Crambe crambe led to the iso... more The full chemical reinvestigation of the Mediterranean marine sponge Crambe crambe led to the isolation and structural characterization of 11 crambescin derivatives, including 8 new compounds, together with the known crambescidin 816. HRMS/MS studies allowed the complete assignment of the alkyl chain lengths of these guanidine alkaloids while the absolute configurations of all compounds were inferred from the comparison between experimental and theoretical circular dichroism spectra. Crambescidin 816 was proven to be more cytotoxic against neuronal cell lines than crambescin C1. ; Tel: +33 493377708 { Electronic supplementary information (ESI) available: NMR and HRMS spectra are given for compounds 1-11. See