ERASSTRI - European risk assessment study on synthetic turf rubber infill - Part 3: Exposure and risk characterisation.

As the final part of a Europe-wide study on the risk from synthetic turf infill consisting of rubber granules derived from end-of-life tyres (ELT), exposure of sportspeople was assessed and compared with health-based reference values for various chemical substances. Based on information from previous project phases, exposure scenarios were established and exposure was calculated for oral, dermal and inhalation routes. Calculated cancer risks for exposure to polycyclic aromatic hydrocarbons were below 1:1 million. Risk characterisation ratios (RCRs) for non-carcinogenic substances were below 1, indicating no health concerns. For 2-hydroxybenzothiazole no toxicological data were found from which to derive a substance-specific reference value. A threshold-of-toxicological concern approach revealed maximum RCRs slightly above 1, which are acceptable, given the conservativism of the approach. ERASSTRI substantially improved the data available for assessing human health risks from using ELT-derived infill material. Overall, no health concerns could be identified for the use of synthetic turfs with ELT-derived infill material.

ERASSTRI - European Risk Assessment Study on Synthetic Turf Rubber Infill - Part 2: Migration and monitoring studies.

End-of-life tyre (ELT)-derived rubber granules are used as synthetic turf infill on sports fields. They contain various chemical substances and there are concerns that exposure to these substances might be harmful for human health. In this second part of a Europe-wide study to address these concerns migration of substances from rubber granules to artificial body fluids (sweat, saliva, gastric juice) was tested and exposure measurements at sports fields were performed to improve the database for exposure assessment. Some PAHs, aluminium, cobalt, benzothiazole, tert-butylamine, MIBK, 4-tert-octylphenol, bisphenol A, and the phthalates DINP and DEHP were found in at least some samples of sweat simulant. The migration rates calculated with these data were used to inform the dermal exposure assessment. In artificial saliva and gastric juice, only aluminium, cobalt, 4-tert-octylphenol and MIBK were detected and migrated fractions were calculated. Bioaccessibility from rubber granules in the gastrointestinal tract was estimated conservatively, assuming complete availability for most substances. In addition, air samples from 17 sports fields in six European countries were analysed. There were no increased concentrations of metals (aluminium, cobalt), PAHs, or other semivolatile substances in air samples, but some volatiles (MIBK: 95th percentile: 18 µg/m3, benzothiazole: 95th perc.: 7 µg/m3, tert-butylamine: 95th perc.: 31 µg/m3, 2-heptanone: 95th perc.: 0.4 µg/m3, cyclohexanone: 95th perc.: 1.5 µg/m3, and saturated aliphatic hydrocarbons >C9: 95th perc.: 26 µg/m3) were slightly increased in a few samples. In addition, skin wipe samples were obtained from 43 sportspeople after playing on synthetic turfs. Only aluminium was detected above the limit of quantification in these samples (95th perc.: 0.84 mg/sample). These data are important input for risk characterisation as performed in the final study phase. Bioaccessibility data are used for estimating oral and dermal exposure of sportspeople, and air measurements are essential for inhalation exposure assessment.

ERASSTRI - European Risk Assessment Study on Synthetic Turf Rubber Infill - Part 1: Analysis of infill samples.

End-of-life tyre (ELT)-derived rubber granules are used as synthetic turf infill on sports fields. They contain various chemical substances and there are concerns that exposure to these substances might be harmful for human health. This Europe-wide risk assessment study addresses these concerns. As the first part, chemical substances in samples from recycling companies and from sports fields were analysed. 86 coated and non-coated ELT granule samples from sites in 14 European countries were investigated, together with ten non-ELT materials. An extensive list of potentially relevant substances was compiled, and the infill materials were analysed for these substances, using GC and HPLC methods. Volatilisation of substances was studied in emission chambers. Polycyclic aromatic hydrocarbons (sum of 8 REACH PAHs) were identified at average concentrations below 10 mg/kg. Substances found at higher concentrations in rubber granules were aluminium (arithmetic mean in uncoated samples from sports fields 5383 mg/kg) and cobalt (168 mg/kg), benzothiazole (48 mg/kg) and 2-hydroxybenzothiazole (34 mg/kg), 6PPD (571 mg/kg) and DPG (51 mg/kg), and 4-tert-octylphenol (14 mg/kg). In addition, the following volatiles were found to evaporate from crumb rubber in emission chambers: benzothiazole, tert-butylamine, cyclohexanone, methyl isobutyl ketone, 2-heptanone and saturated aliphatic hydrocarbons higher than C9. With this comprehensive survey we created a profound database on concentrations of chemical substances in ELT-derived infill material, which is essential for a reliable risk assessment. The results were used to inform subsequent investigations (migration studies, exposure monitoring survey).

Detoxification of VX and Other V-Type Nerve Agents in Water at 37 °C and pH†7.4 by Substituted Sulfonatocalix[4]arenes.

Sulfonatocalix[4]arenes with an appended hydroxamic acid residue can detoxify VX and related V-type neurotoxic organophosphonates with half-lives down to 3 min in aqueous buffer at 37 °C and pH 7.4. The detoxification activity is attributed to the millimolar affinity of the calixarene moiety for the positively charged organophosphonates in combination with the correct arrangement of the hydroxamic acid group. The reaction involves phosphonylation of the hydroxamic acid followed by a Lossen rearrangement, thus rendering the mode of action stoichiometric rather than catalytic. Nevertheless, these calixarenes are currently the most efficient low-molecular-weight compounds for detoxifying persistent V-type nerve agents under mild conditions. They thus represent lead structures for novel antidotes that allow treatment of poisonings by these highly toxic chemicals.

Kinetic analysis of interactions of amodiaquine with human cholinesterases and organophosphorus compounds.

Standard therapy of poisoning by organophosphorus compounds (OP) is a combined administration of an anti-muscarinic drug (e.g. atropine) and an oxime as reactivator of inhibited acetylcholinesterase (AChE). Limited efficacy of clinically used oximes against a variety of OPs was shown in numerous studies, calling for research on novel reactivators of OP-inhibited AChE. Recently, reactivation of OP-inhibited AChE by the antimalarial drug amodiaquine was reported. In the present study, amodiaquine and its interactions with human cholinesterases in presence or absence of OP nerve agents was investigated in vitro. Thereby, reversible inhibition of human cholinesterases by amodiaquine (AChE ≫ BChE) was observed. Additionally, a mixed competitive-non-competitive inhibition type of amodiaquine with human AChE was determined. Slow and partial reactivation of sarin-, cyclosarin- and VX-inhibited cholinesterases by amodiaquine was recorded, amodiaquine failed to reactivate tabun-inhibited human cholinesterases. Amodiaquine, being a potent, reversible AChE inhibitor, was tested for its potential benefit as a pretreatment to prevent complete irreversible AChE inhibition by the nerve agent soman. Hereby, amodiaquine failed to prevent phosphonylation and resulted only in a slight increase of AChE activity after removal of amodiaquine and soman. At present the molecular mechanism of amodiaquine-induced reactivation of OP-inhibited AChE is not known, nevertheless amodiaquine could be considered as a template for the design of more potent non-oxime reactivators.

A novel fluorogenic probe for the investigation of free thiols: Application to kinetic measurements of acetylcholinesterase activity.

A novel coumarin-derived thiol probe, based on the thiol-promoted cleavage of a quenching 2,4-dinitrobenzenesulfonyl group is described. The probe shows a sensitive fluorescence turn-on and sufficient solubility in aqueous environments. As a proof of concept, a new assay for AChE activity was developed as a useful addition to the established Ellman method. The observed reaction kinetics followed an asymmetric sigmoidal pattern and were successfully evaluated applying a three parameter Gompertz equation. Providing a linear relationship between the detected fluorescence formation curves and corresponding enzyme activities, this probe appears as a valuable tool for AChE activity measurements.

Kinetics of pesticide degradation by human fresh frozen plasma (FFP) in vitro.

There is an ongoing debate about the benefit of fresh frozen plasma (FFP) infusion in organophosphorus (OP) pesticide-poisoned patients. This prompted us to investigate the kinetics of OP pesticide degradation by FFP with an enzymatic assay in vitro. Degradation was rapid with shortest half-lives of 19.5s for chlorpyrifos-oxon, 6.3min for paraoxon-ethyl and 17.9min for dichlorvos. Heptenophos (78.0min), mevinphos (101.8min), profenofos (162.3min) and malaoxon (179.7min) showed half-lives of up to 3h. Substantial longer degradation half-lives of 69.7-80.8h were determined with chlorfenvinphos and bromfenvinphos. Methamidophos and omethoate showed no degradation by FFP indicated by half-lives similar to spontaneous hydrolysis. In conclusion, degradation by FFP depends on the particular OP pesticide and the used FFP batch.

Detoxification of alkyl methylphosphonofluoridates by an oxime-substituted ß-cyclodextrin--an in vitro structure-activity study.

Detoxification rates of a series of alkyl methylphosphonofluoridates by an oxime-substituted ß-cyclodextrin (ß-CD) were assessed quantitatively by using an AChE inhibition assay. The cyclodextrin (CD) derivative was identified in previous work as a highly active cyclosarin scavenger. Here, a structure-activity relationship was established by investigating the effect of this CD on the detoxification of sarin derivatives differing in the structure of the alkoxy residue. The results show that detoxification rates correlate with the steric bulk and chain length of the alkoxy group in the organophosphonate (OP). OPs with larger, more bulky residues are detoxified more rapidly, with the exception of soman, which is bearing a pinacolyloxy side chain. In addition, the substituted CD was in every case more active than unsubstituted, native ß-CD with up to a 400-fold difference. Comparing the kinetic results obtained with the known thermodynamic stabilities of related ß-CD complexes indicate that detoxification rates generally increase when the alkoxy residue on the OP is exchanged by a residue, which forms a more stable complex with ß-CD. This correlation lends support to the proposed mode of action of the substituted CD, involving initial complexation of the OP followed by reaction between the CD and the OP. The moderate to high efficacy on the detoxification of sarin derivatives suggests the potential applicability of this CD as a small molecule scavenger for G-type nerve agents.

Tabun scavengers based on hydroxamic acid containing cyclodextrins.

Arrangement of several hydroxamic acid-derived substituents along the cavity of a cyclodextrin ring leads to compounds that detoxify tabun in TRIS-HCl buffer at physiological pH and 37.0 °C with half-times as low as 3 min.

Kinetic interactions of a homologous series of bispyridinium monooximes (HGG oximes) with native and phosphonylated human acetylcholinesterase.

Inhibition of acetylcholinesterase (AChE) is the main toxic mechanism of organophosphorus compounds (OP) and reactivation of OP-inhibited AChE by oximes is a mainstay of antidotal treatment. The inadequate efficacy of clinically used oximes led to the synthesis of numerous new compounds in the past decades to identify more effective reactivators. Despite of extensive in vitro reactivation studies the structural features for the development of effective oximes are not well understood. In the present study we investigated the kinetic interactions of a homologous series of bispyridinium monoximes bearing C1 to C12 alkylketone groups on the second pyridinium ring with native and cyclosarin-inhibited human AChE. We observed a correlation of the length of the alkyl side chain with an up to 20-fold increased affinity towards native AChE. The effect of the alkyl side chain on the affinity and reactivity towards phosphonylated AChE was moderate, except of a markedly reduced reactivity of C10 and C12 oximes. In comparison to the reference oxime HI-6 all HGG oximes had a lower reactivating potency and these oximes are not considered as promising compounds for the reactivation of cyclosarin-inhibited AChE.