Even though the genetic attributes suggest presence of multiple degradation pathways, most of rhodococci are known to transform PCBs only via regular biphenyl (bph) pathway. Using GC-MS analysis, we ...monitored products formed during transformation of 2,4,4′-trichlorobiphenyl (PCB-28), 2,2′,5,5′-tetrachlorobiphenyl (PCB-52) and 2,4,3′-trichlorobiphenyl (PCB-25) by previously characterized PCB-degrading rhodococci Z6, T6, R2, and Z57, with the aim to explore their metabolic pleiotropy in PCB transformations. A striking number of different transformation products (TPs) carrying a phenyl ring as a substituent, both those generated as a part of the bph pathway and an array of unexpected TPs, implied a curious transformation ability. We hypothesized that studied rhodococcal isolates, besides the regular one, use at least two alternative pathways for PCB transformation, including the pathway leading to acetophenone formation (via 3,4 (4,5) dioxygenase attack on the molecule), and a third sideway pathway that includes stepwise oxidative decarboxylation of the aliphatic side chain of the 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate. Structure of the identified chlorinated benzoic acids and acetophenones allowed us to hypothesize that the first two pathways were the outcome of a ring-hydroxylating dioxygenase with the ability to attack both the 2,3 (5,6) and the 3,4 (4,5) positions of the biphenyl ring as well as dechlorination activity at both, -ortho and -para positions. We propose that several TPs produced by the bph pathway could have caused the triggering of the third sideway pathway. In conclusion, this study proposed ability of rhodococci to use different strategies in PCB transformation, which allows them to circumvent potential negative aspect of TPs on the overall transformation pathway.
•Tested rhodococci use complex metabolic hub for PCB transformation.•Rhodococci use regular bph pathway in PCB transformation.•Alternative pathways works via production of acetophenones.•Third pathway includes stepwise oxidative decarboxylation of the aliphatic side chain of the HOPDA.•Rhodococci harbor specific ring-hydroxylating dioxygenase with dechlorination ability.
As part of our OPENTOX project, we evaluated the incidence and mass concentrations of multiclass pesticide residues in 23 river/stream water samples collected in urban and agricultural areas of ...northwest Croatia at various points of the pesticide application season in 2015. The study included 16 compounds of five herbicide classes and seven compounds of three insecticide classes. Pesticide residues were accumulated from water by solid-phase extraction and analysed using high performance liquid chromatography with UV-diode array detection and/or gas chromatography-mass spectrometry. Herbicide residues were more common than the insecticide ones, and, as expected, they peaked in the middle of the application season. Metolachlor showed the highest concentrations and was found in 91 % of all samples, followed by terbuthylazine, found in 70 % of the samples. The highest total mass concentration of detected pesticides was measured in the water samples of the Krapina (3992 ng/L) and Sutla (3455 ng/L) collected in rural areas with intensive agriculture. Our findings strongly speak in favour of continued monitoring of surface waters and possibly extending the list of priority water pollutants.
This review summarises our two decades of polychlorinated biphenyl (PCB) monitoring in different marine organisms along the eastern Adriatic Sea. The aim was to gain an insight into the trends of PCB ...distribution in order to evaluate the effectiveness of past and current legislation and suggest further action. Here we mainly focus on PCB levels in wild and farmed Mediterranean mussels, wild and farmed bluefin tuna, loggerhead sea turtles, common bottlenose dolphins, and small pelagic fish. The use of artificial intelligence and advanced statistics enabled an insight into the influence of various variables on the uptake of PCBs in the investigated organisms as well as into their mutual dependence. Our findings suggest that PCBs in small pelagic fish and mussels reflect global pollution and that high levels in dolphins and wild tuna tissues raise particular concern, as they confirm their biomagnification up the food chain. Therefore, the ongoing PCB monitoring should focus on predatory species in particular to help us better understand PCB contamination in marine ecosystems in our efforts to protect the environment and human health.
We studied the occurrence and levels of hexachlorobenzene, α-, β-, and γ-hexachlorocyclohexane, 4,4'-DDT, 4,4'-DDE, 4,4'-DDD, and 17 PCBs (six indicator and eleven other toxicologically significant ...congeners) in PM.sub.10 and/or PM.sub.2.5 particle fractions collected between 2000 and 2003 and in 2010 at a site in the northern residential part of Zagreb, Croatia. Twenty-four-hour particle samples were collected on glass or quartz microfibre filters from approximately 100 m.sup.3 of ambient air per filter. Filters with particles collected over seven consecutive days were combined for ultrasonic extraction with 1: 1 acetone : n-hexane mixture followed by capillary gas chromatography with electron capture detection. In the monitored periods, the mass concentrations of organochlorine compounds in atmospheric particles were characteristic of global environmental pollution and showed a decreasing trend. Local input was observed only for γ-hexachlorocyclohexane. There were no pronounced seasonal variations in the mass fraction levels of any pesticide or PCB in airborne particles. A decreasing trend in the mass concentrations of some compounds with higher air temperatures was mostly related to the lower particle concentrations in warmer seasons and, consequently, to less particle-bound organochlorine compounds in the atmosphere. Keywords: organochlorine pesticides, PM.sub.10, PM.sub.2.5, polychlorinated biphenyls
The occurrence and distribution of 11 organochlorine pesticides (OCPs) and their degradation products as well as of 17 polychlorinated biphenyl congeners (PCBs) were investigated for the first time ...in sediments of three (Lake Prošće, Lake Kozjak, Lake Kaluđerovac) out of 16 cascading karst lakes within the protected area of the Plitvice Lakes National Park in central Croatia. The 15-cm-long sediment cores were divided for analysis into three 5-cm-long segments. The abundance and levels of sediment-associated OCPs and PCBs were evaluated with respect to sampling location and sediment depth, presumed age of deposition, and organic carbon content. The burden of sediments with OCPs and PCBs decreased downstream with the highest mass fractions measured in the uppermost Lake Prošće (total OCPs 2.72–5.86 μg kg
−1
d.m., total PCBs 0.37–1.78 µg kg
−1
d.m.) and the lowest in Lake Kaluđerovac (total OCPs 0.30–0.58 μg kg
−1
d.m., total PCBs 0.07–0.12 µg kg
−1
d.m.). The predominant organochlorine pollutants were DDT-type compounds (total DDX,
w
= 0.30–5.72 µg kg
−1
d.m.) with
p,p
′-DDE and
p,p
′-DDD accounting for up to 100% and 50%, respectively, of the total DDX. The findings indicated an old input of
p,p
′-DDT that largely converted to its degradation products. The OCP and PCB mass fractions in the Plitvice lake sediments were at trace levels characteristic for preserved pristine natural environments with no or limited anthropogenic impact wherein long-range atmospheric transport is considered as their main source.
The recognition of certain herbicides as endocrine disrupting compounds has raised concerns due to their ability to interfere with the normal functioning of the endocrine system, which regulates ...various physiological processes in organisms. The objective of this study was to assess the possible human health risks associated with terbuthylazine and endocrine-disrupting herbicides atrazine, acetochlor, and metolachlor in the drinking, surface, and groundwater of the Zagreb city region, Croatia. We relied on advanced statistical methods and principal component analysis (PCA), which revealed higher levels of atrazine and acetochlor in drinking and groundwater samples and higher presence of metolachlor and terbuthylazine in surface waters. To evaluate the danger to human health, various exposure scenarios have been assessed. The risk of direct human exposure to analyzed herbicides through drinking or bathing with drinking (tap) or groundwater, as well as from recreational activities like swimming in rivers, streams, and lakes, has been quantified. In addition to these direct exposure scenarios, indirect ones based on consumer goods, fruits, and vegetables, treated with surface and groundwater for irrigation, were assessed to investigate the danger to human health. Judging by the reported herbicide levels there was no significant risk of carcinogenic (CR ≤ 1 × 10
−6
) or non-carcinogenic (HI < 1) diseases, not even when we assessed the so-called “cocktail effect” of combined the herbicide exposure in different waters.
This review article summarizes our research of persistent organic pollutants (POPs) in human milk from Croatian mothers over the last few decades. Our studies make up the bulk of all POPs research in ...human milk in Croatia and show a state-of-the art in the research area. The first investigations were made in 1970's. Aim of our review article is to document the comprehensive results over several decades as the best tool to: 1.) contribute to understanding of POPs and their potential health risks, 2.) evaluate effectiveness of legislative bans and restrictions on human exposure to POPs in Croatia, and 3.) to suggest further actions. In our review we discuss: 1.) Human milk between 2011 and 2014 - evaluation of interrelations of organochlorine pesticides (OCP) and polychlorinated biphenyls (PCB) in human milk and their association with the mother's age and parity using artificial intelligence methods; and our yet unpublished research data on health risks for infants assessed through daily PCB and OCP intake. 2.) Time trends of PCB and OCP in human milk between 1976 and 2014. 3.) polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran (PCDD/F) in human milk in 2000., and yet unpublished data on PCDD/F and polybrominated diphenyl ethers (PBDE) in 2014.
•Decreasing trend between 1976 and 2014 for PCBs, β-HCH, p,p'-DDE.•Decreasing trend between 1976 and 2014 for HCB.•Machine learning methodologies charaterised POPs interrelations.•Ortho position in the biphenyl ring is essential for PCB profiles in breast milk.•Highlighted persistency of 2,3,4,7,8-PeCDF and indicated recent input of p,p'-DDT.
The fluorinated bis-pyridinium oximes were designed and synthesized with the aim of increasing their nucleophilicity and potential to reactivate phosphorylated human recombinant acetylcholinesterase ...(AChE) and human purified plasmatic butyrylcholinesterase (BChE) in relation to chlorinated and non-halogenated oxime analogues. Compared to non-halogenated oximes, halogenated oximes showed lower pKa of the oxime group (fluorinated < chlorinated < non-halogenated) along with higher level of oximate anion formation at the physiological pH, and had a higher binding affinity of both AChE and BChE. The stability tests showed that the fluorinated oximes were stable in water, while in buffered environment di-fluorinated oximes were prone to rapid degradation, which was reflected in their lower reactivation ability. Mono-fluorinated oximes showed comparable reactivation to non-halogenated (except asoxime) and mono-chlorinated oximes in case of AChE inhibited by sarin, cyclosarin, VX, and tabun, but were less efficient than di-chlorinated ones. The same trend was observed in the reactivation of inhibited BChE. The advantage of halogen substituents in the stabilization of oxime in a position optimal for in-line nucleophilic attack were confirmed by extensive molecular modelling of pre-reactivation complexes between the analogue oximes and phosphorylated AChE and BChE. Halogen substitution was shown to provide oximes with additional beneficial properties, e.g., fluorinated oximes gained antioxidative capacity, and moreover, halogens themselves did not increase cytotoxicity of oximes. Finally, the in vivo administration of highly efficient reactivator and the most promising analogue, 3,5-di-chloro-bispyridinium oxime with trimethylene linker, provided significant protection of mice exposed to sarin and cyclosarin.
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•Halogenated pyridinium oximes have decreased pKa and are efficiently forming oximate nucleophiles.•Halogenated pyridinium oximes are able to reactivate acetylcholinesterase inhibited by nerve agents in vitro.•Halogenated pyridinium oximes are able to simultaneously reactivate butyrylcholinesterase inhibited by nerve agents in vitro.•Bis-chlorinated oxime with trimethylene linker is able to protect mice against sarin or cyclosarin challenge in vivo.
This article investigated the multi-year polychlorinated biphenyl (PCB) burden of the sediment collected along the Kupa River flow in Croatia using the bedload sediment transport model. Kupa, as the ...natural border between Croatia and Slovenia, belongs to the water system Krupa (Slovenia) → Lahinja (Slovenia) → Kupa (Croatia) → Sava → Danube → Black Sea. From 1962 to 1985, the total quantity of waste calculated for pure PCBs, released by a capacitor manufacturer into the environment within various locations of the Krupa River in Slovenia, was 70 tons. Krupa River (Slovenia) has become one of the most PCB-polluted rivers in Europe, and consequently, PCBs have been detected in the Kupa River (Croatia). Model application revealed that contamination of the Kupa River (Croatia) started significantly earlier than 1983, when a high concentration of PCB was detected for the first time in the Krupa River (Slovenia), with probably significantly higher sediment concentrations at the upstream boundary of the Kupa. A slow concentration changes and PCB accumulation in the sediment should be expected downstream compared to the upstream boundary, governed mainly by high flow events. The PCBs in sediments from 2020/2021 are markedly different after the Lahinja confluence with Kupa (0.2–0.6 μg kg
−1
vs. 1.4–34.3 μg kg
−1
). Measurements of PCBs in Kupa sediment suggest that the intake of PCB has not yet been completely stopped, which should be confirmed by detailed monitoring in the future. The contamination situation observed in the Kupa River represents an excellent example of the persistency of PCBs in the environment.
The frequency and mass concentrations of 13 herbicide micropollutants (triazines, phenylureas, chloroacetanilides and trifluralin) were investigated during 2014 in surface, ground and drinking waters ...in the area of the city of Zagreb and its suburbs. Herbicide compounds were accumulated from water by solid-phase extraction using either octadecylsilica or styrene-divinylbenzene sorbent cartridges and analysed either by high-performance liquid chromatography with UV-diode array detector or gas chromatography with mass spectrometric detection. Atrazine was the most frequently detected herbicide in drinking (84 % of samples) and ground (61 % of samples) waters in mass concentrations of 5 to 68 ng L
−1
. It was followed by metolachlor and terbuthylazine, the former being detected in 54 % of drinking (up to 15 ng L
−1
) and 23 % of ground (up to 100 ng L
−1
) waters, and the latter in 45 % of drinking (up to 20 ng L
−1
) and 26 % of ground (up to 25 ng L
−1
) water samples. Acetochlor was the fourth most abundant herbicide in drinking waters, detected in 32 % of samples. Its mass concentrations of 107 to 117 ng L
−1
in three tap water samples were the highest of all herbicides measured in the drinking waters. The most frequently (62 % of samples) and highly (up to 887 ng L
−1
) detected herbicide in surface waters was metolachlor, followed by terbuthylazine detected in 49 % of samples in mass concentrations of up to 690 ng L
−1
, and atrazine detected in 30 % of samples in mass concentrations of up to 18 ng L
−1
. The seasonal variations in herbicide concentrations in surface waters were observed for terbuthylazine, metolachlor, acetochlor, chlortoluron and isoproturon with the highest concentrations measured from April to August.
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