Transformation of Phenanthrene by Mycobacterium sp. ELW1 and the Formation of Toxic Metabolites

The ability of Mycobacterium sp. ELW1, a novel microbe capable of alkene oxidation, to co-metabolize phenanthrene (PHE) was studied. ELW1 was able to completely co-metabolize PHE, at different concentrations below its water solubility limit, in an aqueous environment. The alkene monooxygenases in ELW1, used to initiate oxidation of PHE, were effectively inhibited by 1-octyne despite some PHE transformation observed. PHE metabolites consisted of only hydroxyphenanthrenes (OHPHEs) with trans-9,10-dihydroxy-9,10-dihydrophenanthrene (trans-9,10-PHE), the primary product, comprising more than 90% of the total metabolites formed in both PHE-exposed cells and 1-octyne controls. Mass balance was estimated by summing the zero-order formation rates of OHPHE metabolites and comparing these to the zero-order transformation rates PHE in PHE-exposed cells. The transformation rates of PHE and were in good agreement with the formation rates of the metabolites. PHE transformation followed first-order rates that, when normalized by biomass, were in the range of those estimated by the ratio of the Michaelis-Menten kinetic variables of maximum transformation rate (k[subscript max]) to the half-saturation constant (K[subscript s]). Estimated values for k[subscript max] to K[subscript s] obtained through both non-linear and linearization methods resulted in k[subscript max]/K[subscript s] estimates that were a factor of ~3 lower compared to experimental values. Both experimental and estimated values of k[subscript max], K[subscript s], and k[subscript max]/K[subscript s] were 2-3 magnitudes lower than literature values determined for microbes other than Mycobacterium sp. using different models that incorporated additional parameters. OHPHE standards, including 1-hydroxyphenanthrene (1-PHE), 3-hydroxyphenanthrene (3-PHE), 4-hydroxyphenanthrene (4-OHE), 9-hydroxyphenanthrene (9-PHE), and 1,9-dihydroxyphenanthrene (1,9-PHE), were developmentally toxic to embryonic zebrafish. However, PHE and trans-9,10- PHE. were not toxic. OHPHE metabolite mixtures formed by ELW1 were also tested for toxicity using embryonic zebrafish. The embryonic zebrafish were exposed to OHPHE metabolite mixtures that were at least 1.5 times less than the concentration need to elicit a toxic response. However, toxicity was observed in the two latest time points, 76 and 122 hr, in PHE-exposed cells. The toxicity may have been caused by an unidentified toxic metabolite

Comparison between lichen, conifer needles, resin-based passive air sampling devices (PASDs), and snow to monitor semi-volatile organic compounds (SOCs) in the atmosphere

The purpose of this research was to compare four different media that were used to monitor SOC atmospheric concentrations in remote ecosystems. The accumulation of semi-volatile organic compounds, including pesticides, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), was investigated in lichen, 2-year old conifer needles, resin-based passive air sampling devices (PASDs), and snow. In addition, an analytical method for the trace analysis of these SOCs in lichen, conifer needles, and SOCs in PASDs, was developed and validated. To evaluate the preferential accumulation of SOCs in these media, lichen and conifer needles were collected in 2004, PASDs were collected in 2006 after a 1-year exposure period, and snowpack was collected in spring 2003 and 2004 from the same sites in 5 Western U.S. national parks (NPs), including Sequoia NP, Rocky Mtn. NP, Olympic NP, Glacier NP, and Denali NP. Endosulfan sulfate, a degradation product of the pesticide endosulfan, preferentially accumulated in lichen. Hexachlorobenzene (HCB) and fluorene preferentially accumulated in PASDs, and dacthal, chlorpyrifos, dieldrin, acenapthene, and benzo[ghi]perylene preferentially accumulated in snow. Hexachlorocyclohexanes (HCHs) and PCBs did not preferentially accumulate in any one medium. The influence of SOC physical-chemical properties, including air-water partition coefficient (KAW), octanol-air partition coefficient (Log KOA) and the estimated SOC fraction in the particle phase in the atmosphere (Φ), on accumulation in each medium was also investigated. The effect of SOC physical-chemical properties on medium accumulation was evaluated at all sites from which lichen, conifer needles, PASDs, and snow were collected (82, 85, 33, and 30 sites, respectively). These SOC physical-chemical properties significantly influenced the accumulation of dacthal, endosulfans, trans-chlordane, nonachlors, and several PAHs in several of the media. The results from this research indicate that pesticides and PAHs preferentially accumulate in snow. Therefore, snow should be used, if possible, in short-term studies (months) of SOC concentrations in the atmosphere of remote ecosystems during the winter months. However, lichen may be used instead of snow in warmer regions or for studies that require longer exposure periods and/or summer months. If lichen is not present in the ecosystem, conifer needles may be used; however the measurement of particle-phase SOCs may be limited by needle structure and estimated method detection limits (EDLs). Finally, PASDs may be used for studies interested in the concentration of specific gas-phase SOCs with residence times in the atmosphere over 1 year and for a more quantitative estimate of atmospheric concentrations

Heterogeneous reactions of particulate matter-bound PAHs and NPAHs with NO3/N2O5, OH radicals, and O3 under simulated long-range atmospheric transport conditions: reactivity and mutagenicity.

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China, and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO3/N2O5, OH radicals, and O3. In general, O3 exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O3 and NO3/N2O5). However, NPAHs were most effectively formed during the Beijing PM exposure to NO3/N2O5. In ambient air, 2-nitrofluoranthene (2-NF) is formed from the gas-phase NO3 radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from the gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO3/N2O5 resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas-phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction

Relative Influence of Trans-Pacific and Regional Atmospheric Transport of PAHs in the Pacific Northwest, US

The relative influences of trans-Pacific and regional atmospheric transport on measured concentrations of polycyclic aromatic hydrocarbons (PAHs), PAH derivatives [Nitro- (NPAH) and Oxy-(OPAH)], organic carbon (OC), and Particulate Matter (PM) less than 2.5 μm in diameter (PM₂.₅) were investigated in the Pacific Northwest, USA in 2010-2011. Ambient high volume PM₂.₅ air samples were collected at two sites in the Pacific Northwest: 1.) Mount Bachelor Observatory (MBO) in the Oregon Cascade Range (2763 m above sea level (asl)) and 2.) Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in the Columbia River Gorge (CRG) (954 m asl). At MBO, the 1,8-dinitropyrene concentration was significantly positively correlated with the time a sampled air mass spent over Asia, suggesting that this NPAH may be a good marker for trans-Pacific atmospheric transport. At CTUIR, NOx, CO₂, and SO₂ emissions from a 585 MW coal fired power plant, in Boardman OR, were found to be significantly positively correlated with PAH, OPAH, NPAH, OC, and PM₂.₅ concentrations. By comparing the Boardman Plant operational time frames when the plant was operating to when it was shut down, the plant was found to contribute a large percentage of the measured PAH (67%), NPAH (91%), OPAH (54%), PM₂.₅ (39%) and OC (38%) concentrations at CTUIR and the CRG prior to Spring 2011 and likely masked trans-Pacific atmospheric transport events to the CRG. Upgrades installed to the Boardman Plant in the spring of 2011 dramatically reduced the plant’s contribution to PAH and OPAH concentrations (by ~72% and ~40%, respectively) at CTUIR and the CRG but not NPAH, PM₂.₅ or OC concentrations

Heterogeneous Reactions of PM-Bound PAHs and NPAHs with NO₃/N₂O₅, OH Radicals, and O₃ under Simulated Long-Range Atmospheric Transport Conditions: Reactivity and Mutagenicity

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO₃/N₂O₅, OH radicals, and O₃ were studied in a laboratory photochemical chamber. Ambient PM[subscript 2.5] and PM₁₀ samples were collected from Beijing, China and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O₃ and OH and NO₃ radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO₃/N₂O₅, OH radicals, and O₃. In general, O₃ exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O₃ and NO₃/N₂O₅). However, NPAHs were most effectively formed during the Beijing PM exposure to NO₃/N₂O₅. In ambient air 2-nitrofluoranthene (2-NF) is formed from gas-phase NO₃ radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO₃/N₂O₅ resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction

Metabolism and Excretion Rates of Parent and Hydroxy-PAHs in Urine Collected after Consumption of Traditionally Smoked Salmon for Native American Volunteers

Few studies have been published on the excretion rates of parent polycyclic aromatic hydrocarbons (PAHs) and hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs) following oral exposure. This study investigated metabolism and excretion rates of 4 parent PAHs and 10 OH-PAHs after the consumption of smoked salmon. Nine members of the Confederated Tribes of the Umatilla Indian Reservation consumed 50 g of traditionally smoked salmon with breakfast and five urine samples were collected during the following 24 hours. The concentrations of OH-PAHs increased from 43.9 µg/g creatinine for 2-OH-Nap to 349 ng/g creatinine for 1-OH-Pyr, 3 to 6 hr post-consumption. Despite volunteers following a restricted diet, there appeared to be a secondary source of naphthalene and fluorene, which led to excretion efficiencies greater than 100%. For the parent PAHs that were detected in urine, the excretion efficiencies ranged from 13% for phenanthrene (and its metabolite) to 240% for naphthalene (and its metabolites). The half-lives for PAHs ranged from 1.4 hr for retene to 3.3 hr for pyrene. The half-lives for OH-PAHs were higher and ranged from 1.7 hr for 9-OH-fluorene to 7.0 hr for 3-OH-fluorene. The concentrations of most parent PAHs, and their metabolites, returned to the background levels 24 hr post-consumption

Organic contaminants in western pond turtles in remote habitat in California

Remote aquatic ecosystems are exposed to an assortment of semivolatile organic compounds (SOCs) originating from current and historic uses, of local and global origin. Here, a representative suite of 57 current- and historic-use pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons were surveyed in the plasma of the western pond turtle (Emys marmorata) and their potential prey items and habitat. California study sites included Sequoia National Park, Whiskeytown National Recreation Area, and Six Rivers National Forest. Each was downstream of undeveloped watersheds and varied in distance from agricultural and urban pollution sources. SOCs were detected frequently in all sites with more found in turtle plasma and aquatic macroinvertebrates in the two sites closest to agricultural and urban sources. Summed PCBs were highest in Whiskeytown National Recreation Area turtle plasma (mean; 1.56 ng/g ww) compared to plasma from Sequoia National Park (0.16 ng/g ww; p = 0.002) and Six Rivers National Forest (0.07 ng/g ww; p = 0.001). While no current-use pesticides were detected in turtle plasma at any site, both current- and historic-use pesticides were found prominently in sediment and macroinvertebrates at the Sequoia National Park site, which is immediately downwind of Central Valley agriculture. SOC classes associated with urban and industrial pollution were found more often and at higher concentrations at Whiskeytown National Recreation Area. These findings demonstrate a range of SOC exposure in a turtle species with current and proposed conservation status and shed additional light on the fate of environmental contaminants in remote watersheds

Comparison of Lichen, Conifer Needles, Passive Air Sampling Devices, and Snowpack as Passive Sampling Media to Measure Semi-Volatile Organic Compounds in Remote Atmospheres.

A wide range of semivolatile organic compounds (SOCs), including pesticides and polycyclic aromatic hydrocarbons (PAHs), were measured in lichen, conifer needles, snowpack and XAD-based passive air sampling devices (PASDs) collected from 19 different U.S. national parks in order to compare the magnitude and mechanism of SOC accumulation in the different passive sampling media. Lichen accumulated the highest SOC concentrations, in part because of its long (and unknown) exposure period, whereas PASDs accumulated the lowest concentrations. However, only the PASD SOC concentrations can be used to calculate an average atmospheric gas-phase SOC concentration because the sampling rates are known and the media is uniform. Only the lichen and snowpack SOC accumulation profiles were statistically significantly correlated (r = 0.552, p-value \u3c0.0001) because they both accumulate SOCs present in the atmospheric particle-phase. This suggests that needles and PASDs represent a different composition of the atmosphere than lichen and snowpack and that the interpretation of atmospheric SOC composition is dependent on the type of passive sampling media used. All four passive sampling media preferentially accumulated SOCs with relatively low air–water partition coefficients, while snowpack accumulated SOCs with higher log KOA values compared to the other media. Lichen accumulated more SOCs with log KOA \u3e 10 relative to needles and showed a greater accumulation of particle-phase PAHs

Organic contaminants in western pond turtles in remote habitat in California.

Remote aquatic ecosystems are exposed to an assortment of semivolatile organic compounds (SOCs) originating from current and historic uses, of local and global origin. Here, a representative suite of 57 current- and historic-use pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons were surveyed in the plasma of the western pond turtle (Emys marmorata) and their potential prey items and habitat. California study sites included Sequoia National Park, Whiskeytown National Recreation Area, and Six Rivers National Forest. Each was downstream of undeveloped watersheds and varied in distance from agricultural and urban pollution sources. SOCs were detected frequently in all sites with more found in turtle plasma and aquatic macroinvertebrates in the two sites closest to agricultural and urban sources. Summed PCBs were highest in Whiskeytown National Recreation Area turtle plasma (mean; 1.56 ng/g ww) compared to plasma from Sequoia National Park (0.16 ng/g ww; p = 0.002) and Six Rivers National Forest (0.07 ng/g ww; p = 0.001). While no current-use pesticides were detected in turtle plasma at any site, both current- and historic-use pesticides were found prominently in sediment and macroinvertebrates at the Sequoia National Park site, which is immediately downwind of Central Valley agriculture. SOC classes associated with urban and industrial pollution were found more often and at higher concentrations at Whiskeytown National Recreation Area. These findings demonstrate a range of SOC exposure in a turtle species with current and proposed conservation status and shed additional light on the fate of environmental contaminants in remote watersheds

Organic contaminants in western pond turtles in remote habitat in California.

Remote aquatic ecosystems are exposed to an assortment of semivolatile organic compounds (SOCs) originating from current and historic uses, of local and global origin. Here, a representative suite of 57 current- and historic-use pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons were surveyed in the plasma of the western pond turtle (Emys marmorata) and their potential prey items and habitat. California study sites included Sequoia National Park, Whiskeytown National Recreation Area, and Six Rivers National Forest. Each was downstream of undeveloped watersheds and varied in distance from agricultural and urban pollution sources. SOCs were detected frequently in all sites with more found in turtle plasma and aquatic macroinvertebrates in the two sites closest to agricultural and urban sources. Summed PCBs were highest in Whiskeytown National Recreation Area turtle plasma (mean; 1.56 ng/g ww) compared to plasma from Sequoia National Park (0.16 ng/g ww; p = 0.002) and Six Rivers National Forest (0.07 ng/g ww; p = 0.001). While no current-use pesticides were detected in turtle plasma at any site, both current- and historic-use pesticides were found prominently in sediment and macroinvertebrates at the Sequoia National Park site, which is immediately downwind of Central Valley agriculture. SOC classes associated with urban and industrial pollution were found more often and at higher concentrations at Whiskeytown National Recreation Area. These findings demonstrate a range of SOC exposure in a turtle species with current and proposed conservation status and shed additional light on the fate of environmental contaminants in remote watersheds