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Uta Jappe - One of the best experts on this subject based on the ideXlab platform.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part i reaction frequencies
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    SummaryBackground Epoxy resin systems (ERSs), consisting of resins, reactive diluents, and hardeners, are indispensable in many branches of industry. In order to develop less sensitizing ERS formulations, knowledge of the sensitizing properties of single components is mandatory. Objectives To analyse the frequency of sensitization in the patients concerned, as one integral part of a research project on the sensitizing potency of epoxy resin compounds (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, and a comparison of reaction frequencies with (surrogate) exposure data, were performed. Results Almost half of the patients sensitized to epoxy resin were additionally sensitized to reactive diluents or hardeners. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether was the most frequent allergen, followed by 1,4-butanediol diGlycidyl Ether, Phenyl Glycidyl Ether, and p-tert-butylPhenyl Glycidyl Ether. Among the hardeners, m-xylylene diamine (MXDA) and isophorone diamine (IPDA) were the most frequent allergens. According to the calculated exposure-related frequency of sensitization, MXDA seems to be a far more important sensitizer than IPDA. Up to 60% of the patients sensitized to hardeners and 15–20% of those sensitized to reactive diluents do not react to epoxy resin. Conclusions In cases of suspected contact allergy to an ERS, a complete epoxy resin series must be patch tested from the start.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part ii concomitant reactions
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    Summary Background Beside the basic resins, reactive diluents and hardeners are important sensitizers in epoxy resin systems (ERSs). Because of chemical similarities, immunological cross-reactivity may occur. Objectives To analyse concomitant reactivity among reactive diluents and hardeners in the patients concerned, as one integral part of a research project on the sensitizing capacity of ERSs (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, was performed. Results There was close concomitant reactivity to 1,6-hexanediol diGlycidyl Ether and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE), and to Phenyl Glycidyl Ether (PGE) and cresyl Glycidyl Ether (CGE), whereas reactions to p-tert-butylPhenyl Glycidyl Ether occurred more independently from those to PGE and CGE. Concomitant reactions to butyl Glycidyl Ether and 1,4-BDDGE may point to a common allergenic compound derived from the metabolism of 1,4-BDDGE. Among the structurally more diverse group of hardeners, there was no evidence of immunological cross-reactions. Conclusions More detailed knowledge of cross-reactivity among ERS components facilitates the interpretation of patch test results and will allow safer ERSs to be composed in the future.

  • an attempt to improve diagnostics of contact allergy due to epoxy resin systems first results of the multicentre study epox 2002
    Contact Dermatitis, 2004
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Uta Jappe, Heinrich Dickel, P Koch, Peter J Frosch, Axel Schnuch, Wolfgang Uter
    Abstract:

    Epoxy resin systems (ERSs) are a frequent cause of occupational allergic contact dermatitis. Sensitization occurs not only to the resins, but also to hardeners and reactive diluents. However, only a fraction of the ERS components currently in use are available for patch testing. With the multicentre study EPOX 2002, we attempted to improve diagnostics in this field by patch testing with components currently used in ERSs. During the first study period (October 2002 to July 2003), in addition to commercially available ERS patch test substances, 16 study substances (1 resin, 9 hardeners and 6 reactive diluents) were patch tested in 70 patients with suspected contact allergy due to ERSs and 22 patients with a prior positive patch test reaction to epoxy resin (ER) in the standard series. Most frequently, allergic reactions to ER based on diGlycidyl Ether of bisphenol A and F were observed (55.2% and 43.7%, respectively). Agreement between positive reactions to both resins, which can be explained by immunological cross-sensitization and/or coexposure, was substantial [Cohen's kappa 0.65 (95% CI: 0.49-0.80)]. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether (1,6-HDDGE) and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE) were the most frequent allergens, with 19.5% and 18.4% positive reactions, respectively. Although agreement between positive reactions to 1,6-HDDGE and 1,4-BDDGE was even better than with the 2 resins, the sample size is considered too small to decide reliably whEther 1,6-HDDGE alone could serve as a marker allergen for both. Allergic reactions to p-tert-butylPhenyl Glycidyl Ether and to Phenyl Glycidyl Ether (PGE) occurred in 11.5% of the patients tested, with only moderate agreement. All patients positive to cresyl Glycidyl Ether (6.8%) also reacted to PGE. Of the hardeners tested, m-xylylene diamine was the most frequent allergen (13.8%), followed by isophorone diamine (5.7%). No reactions were observed to several substances, the test concentration of which may have been too low and will be increased in the future.

Johannes Geier - One of the best experts on this subject based on the ideXlab platform.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part i reaction frequencies
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    SummaryBackground Epoxy resin systems (ERSs), consisting of resins, reactive diluents, and hardeners, are indispensable in many branches of industry. In order to develop less sensitizing ERS formulations, knowledge of the sensitizing properties of single components is mandatory. Objectives To analyse the frequency of sensitization in the patients concerned, as one integral part of a research project on the sensitizing potency of epoxy resin compounds (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, and a comparison of reaction frequencies with (surrogate) exposure data, were performed. Results Almost half of the patients sensitized to epoxy resin were additionally sensitized to reactive diluents or hardeners. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether was the most frequent allergen, followed by 1,4-butanediol diGlycidyl Ether, Phenyl Glycidyl Ether, and p-tert-butylPhenyl Glycidyl Ether. Among the hardeners, m-xylylene diamine (MXDA) and isophorone diamine (IPDA) were the most frequent allergens. According to the calculated exposure-related frequency of sensitization, MXDA seems to be a far more important sensitizer than IPDA. Up to 60% of the patients sensitized to hardeners and 15–20% of those sensitized to reactive diluents do not react to epoxy resin. Conclusions In cases of suspected contact allergy to an ERS, a complete epoxy resin series must be patch tested from the start.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part ii concomitant reactions
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    Summary Background Beside the basic resins, reactive diluents and hardeners are important sensitizers in epoxy resin systems (ERSs). Because of chemical similarities, immunological cross-reactivity may occur. Objectives To analyse concomitant reactivity among reactive diluents and hardeners in the patients concerned, as one integral part of a research project on the sensitizing capacity of ERSs (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, was performed. Results There was close concomitant reactivity to 1,6-hexanediol diGlycidyl Ether and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE), and to Phenyl Glycidyl Ether (PGE) and cresyl Glycidyl Ether (CGE), whereas reactions to p-tert-butylPhenyl Glycidyl Ether occurred more independently from those to PGE and CGE. Concomitant reactions to butyl Glycidyl Ether and 1,4-BDDGE may point to a common allergenic compound derived from the metabolism of 1,4-BDDGE. Among the structurally more diverse group of hardeners, there was no evidence of immunological cross-reactions. Conclusions More detailed knowledge of cross-reactivity among ERS components facilitates the interpretation of patch test results and will allow safer ERSs to be composed in the future.

  • an attempt to improve diagnostics of contact allergy due to epoxy resin systems first results of the multicentre study epox 2002
    Contact Dermatitis, 2004
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Uta Jappe, Heinrich Dickel, P Koch, Peter J Frosch, Axel Schnuch, Wolfgang Uter
    Abstract:

    Epoxy resin systems (ERSs) are a frequent cause of occupational allergic contact dermatitis. Sensitization occurs not only to the resins, but also to hardeners and reactive diluents. However, only a fraction of the ERS components currently in use are available for patch testing. With the multicentre study EPOX 2002, we attempted to improve diagnostics in this field by patch testing with components currently used in ERSs. During the first study period (October 2002 to July 2003), in addition to commercially available ERS patch test substances, 16 study substances (1 resin, 9 hardeners and 6 reactive diluents) were patch tested in 70 patients with suspected contact allergy due to ERSs and 22 patients with a prior positive patch test reaction to epoxy resin (ER) in the standard series. Most frequently, allergic reactions to ER based on diGlycidyl Ether of bisphenol A and F were observed (55.2% and 43.7%, respectively). Agreement between positive reactions to both resins, which can be explained by immunological cross-sensitization and/or coexposure, was substantial [Cohen's kappa 0.65 (95% CI: 0.49-0.80)]. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether (1,6-HDDGE) and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE) were the most frequent allergens, with 19.5% and 18.4% positive reactions, respectively. Although agreement between positive reactions to 1,6-HDDGE and 1,4-BDDGE was even better than with the 2 resins, the sample size is considered too small to decide reliably whEther 1,6-HDDGE alone could serve as a marker allergen for both. Allergic reactions to p-tert-butylPhenyl Glycidyl Ether and to Phenyl Glycidyl Ether (PGE) occurred in 11.5% of the patients tested, with only moderate agreement. All patients positive to cresyl Glycidyl Ether (6.8%) also reacted to PGE. Of the hardeners tested, m-xylylene diamine was the most frequent allergen (13.8%), followed by isophorone diamine (5.7%). No reactions were observed to several substances, the test concentration of which may have been too low and will be increased in the future.

E Van Den Eeckhout - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the dna adducts of Phenyl Glycidyl Ether in a calf thymus dna hydrolysate by capillary zone electrophoresis electrospray mass spectrometry evidence for phosphate alkylation
    Carcinogenesis, 1998
    Co-Authors: Dieter Deforce, Filip Lemiere, I Hoes, Rebecca E M Millecamps, E L Esmans, A P De Leenheer, E Van Den Eeckhout
    Abstract:

    Calf thymus DNA was reacted in vitro with Phenyl Glycidyl Ether (PGE) and was hydrolysed enzymatically, to the 5'-monophosphate nucleotides using deoxyribonuclease I (DNA-ase I) and nuclease P1. The adducts were concentrated using solid phase extraction (SPE), on a polystyrene divinylbenzene copolymer in order to remove the unmodified nucleotides. The adducts could be identified using capillary zone electrophoresis-electrospray tandem mass spectrometry (CZE ES-MS/MS), using sample stacking. In addition to the base alkylated 2'-deoxynucleotides present in the DNA-hydrolysate, also phosphate alkylated 2'-deoxynucleotide adducts were identified for TMP and dAMP. An additional adduct, dUMP alkylated on the uridine moiety was found originating from the hydrolytic deamination of dCMP alkylated on N3 of the cytosine moiety. Enzymatic hydrolysis using nuclease P1 was incomplete as shown by the presence of dinucleotides alkylated on the base moiety. They were successfully hydrolysed to the corresponding 2'-deoxynucleotides by snake venom phosphodiesterase (SVP). Data are shown indicating that alkylations on the pyrimidine bases were more resistant to enzymatic hydrolysis with nuclease P1 than the purine alkylated products.

  • analysis of the dna damage induced by Phenyl Glycidyl Ether using capillary zone electrophoresis electrospray mass spectrometry
    Analytical Biochemistry, 1998
    Co-Authors: Dieter Deforce, Filip Lemiere, E L Esmans, Andreas De Leenheer, E Van Den Eeckhout
    Abstract:

    Abstract The in vitro adduct formation between Phenyl Glycidyl Ether (PGE) and calf thymus DNA was inves-tigated. Agarose slab gel electrophoresis of DNA incubated with PGE revealed that nearly all high-molecular-weight species were degraded after 10 h of incubation. After DNA precipitation the reaction products present in the supernatant were subjected to a solid-phase extraction on a polystyrene divinylbenzene copolymer, enabling analysis on capillary zone electrophoresis (CZE), using sample stacking. These reaction products were mainly produced during the first 10 h of incubation, indicating that these products result from the DNA degradation. On the other hand, analysis of the adducts present in the enzymatic digest of the DNA pellet revealed that these adducts were formed only after 10 h of incubation. The reaction products present in the DNA supernatant were identified by on-line coupling of CZE to electrospray tandem mass spectrometry. Three major reaction products resulted from phosphate alkylation, as proven by the analysis of the corresponding low-energy CAD product ion mass spectra. This phosphate alkylation results in phosphotriesters which readily hydrolyze, resulting in DNA strand breaks.

Uwe Hillen - One of the best experts on this subject based on the ideXlab platform.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part i reaction frequencies
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    SummaryBackground Epoxy resin systems (ERSs), consisting of resins, reactive diluents, and hardeners, are indispensable in many branches of industry. In order to develop less sensitizing ERS formulations, knowledge of the sensitizing properties of single components is mandatory. Objectives To analyse the frequency of sensitization in the patients concerned, as one integral part of a research project on the sensitizing potency of epoxy resin compounds (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, and a comparison of reaction frequencies with (surrogate) exposure data, were performed. Results Almost half of the patients sensitized to epoxy resin were additionally sensitized to reactive diluents or hardeners. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether was the most frequent allergen, followed by 1,4-butanediol diGlycidyl Ether, Phenyl Glycidyl Ether, and p-tert-butylPhenyl Glycidyl Ether. Among the hardeners, m-xylylene diamine (MXDA) and isophorone diamine (IPDA) were the most frequent allergens. According to the calculated exposure-related frequency of sensitization, MXDA seems to be a far more important sensitizer than IPDA. Up to 60% of the patients sensitized to hardeners and 15–20% of those sensitized to reactive diluents do not react to epoxy resin. Conclusions In cases of suspected contact allergy to an ERS, a complete epoxy resin series must be patch tested from the start.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part ii concomitant reactions
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    Summary Background Beside the basic resins, reactive diluents and hardeners are important sensitizers in epoxy resin systems (ERSs). Because of chemical similarities, immunological cross-reactivity may occur. Objectives To analyse concomitant reactivity among reactive diluents and hardeners in the patients concerned, as one integral part of a research project on the sensitizing capacity of ERSs (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, was performed. Results There was close concomitant reactivity to 1,6-hexanediol diGlycidyl Ether and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE), and to Phenyl Glycidyl Ether (PGE) and cresyl Glycidyl Ether (CGE), whereas reactions to p-tert-butylPhenyl Glycidyl Ether occurred more independently from those to PGE and CGE. Concomitant reactions to butyl Glycidyl Ether and 1,4-BDDGE may point to a common allergenic compound derived from the metabolism of 1,4-BDDGE. Among the structurally more diverse group of hardeners, there was no evidence of immunological cross-reactions. Conclusions More detailed knowledge of cross-reactivity among ERS components facilitates the interpretation of patch test results and will allow safer ERSs to be composed in the future.

  • an attempt to improve diagnostics of contact allergy due to epoxy resin systems first results of the multicentre study epox 2002
    Contact Dermatitis, 2004
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Uta Jappe, Heinrich Dickel, P Koch, Peter J Frosch, Axel Schnuch, Wolfgang Uter
    Abstract:

    Epoxy resin systems (ERSs) are a frequent cause of occupational allergic contact dermatitis. Sensitization occurs not only to the resins, but also to hardeners and reactive diluents. However, only a fraction of the ERS components currently in use are available for patch testing. With the multicentre study EPOX 2002, we attempted to improve diagnostics in this field by patch testing with components currently used in ERSs. During the first study period (October 2002 to July 2003), in addition to commercially available ERS patch test substances, 16 study substances (1 resin, 9 hardeners and 6 reactive diluents) were patch tested in 70 patients with suspected contact allergy due to ERSs and 22 patients with a prior positive patch test reaction to epoxy resin (ER) in the standard series. Most frequently, allergic reactions to ER based on diGlycidyl Ether of bisphenol A and F were observed (55.2% and 43.7%, respectively). Agreement between positive reactions to both resins, which can be explained by immunological cross-sensitization and/or coexposure, was substantial [Cohen's kappa 0.65 (95% CI: 0.49-0.80)]. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether (1,6-HDDGE) and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE) were the most frequent allergens, with 19.5% and 18.4% positive reactions, respectively. Although agreement between positive reactions to 1,6-HDDGE and 1,4-BDDGE was even better than with the 2 resins, the sample size is considered too small to decide reliably whEther 1,6-HDDGE alone could serve as a marker allergen for both. Allergic reactions to p-tert-butylPhenyl Glycidyl Ether and to Phenyl Glycidyl Ether (PGE) occurred in 11.5% of the patients tested, with only moderate agreement. All patients positive to cresyl Glycidyl Ether (6.8%) also reacted to PGE. Of the hardeners tested, m-xylylene diamine was the most frequent allergen (13.8%), followed by isophorone diamine (5.7%). No reactions were observed to several substances, the test concentration of which may have been too low and will be increased in the future.

Holger Lessmann - One of the best experts on this subject based on the ideXlab platform.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part i reaction frequencies
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    SummaryBackground Epoxy resin systems (ERSs), consisting of resins, reactive diluents, and hardeners, are indispensable in many branches of industry. In order to develop less sensitizing ERS formulations, knowledge of the sensitizing properties of single components is mandatory. Objectives To analyse the frequency of sensitization in the patients concerned, as one integral part of a research project on the sensitizing potency of epoxy resin compounds (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, and a comparison of reaction frequencies with (surrogate) exposure data, were performed. Results Almost half of the patients sensitized to epoxy resin were additionally sensitized to reactive diluents or hardeners. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether was the most frequent allergen, followed by 1,4-butanediol diGlycidyl Ether, Phenyl Glycidyl Ether, and p-tert-butylPhenyl Glycidyl Ether. Among the hardeners, m-xylylene diamine (MXDA) and isophorone diamine (IPDA) were the most frequent allergens. According to the calculated exposure-related frequency of sensitization, MXDA seems to be a far more important sensitizer than IPDA. Up to 60% of the patients sensitized to hardeners and 15–20% of those sensitized to reactive diluents do not react to epoxy resin. Conclusions In cases of suspected contact allergy to an ERS, a complete epoxy resin series must be patch tested from the start.

  • sensitization to reactive diluents and hardeners in epoxy resin systems ivdk data 2002 2011 part ii concomitant reactions
    Contact Dermatitis, 2016
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Christoph Skudlik, Uta Jappe
    Abstract:

    Summary Background Beside the basic resins, reactive diluents and hardeners are important sensitizers in epoxy resin systems (ERSs). Because of chemical similarities, immunological cross-reactivity may occur. Objectives To analyse concomitant reactivity among reactive diluents and hardeners in the patients concerned, as one integral part of a research project on the sensitizing capacity of ERSs (FP-0324). Methods A retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2002–2011, was performed. Results There was close concomitant reactivity to 1,6-hexanediol diGlycidyl Ether and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE), and to Phenyl Glycidyl Ether (PGE) and cresyl Glycidyl Ether (CGE), whereas reactions to p-tert-butylPhenyl Glycidyl Ether occurred more independently from those to PGE and CGE. Concomitant reactions to butyl Glycidyl Ether and 1,4-BDDGE may point to a common allergenic compound derived from the metabolism of 1,4-BDDGE. Among the structurally more diverse group of hardeners, there was no evidence of immunological cross-reactions. Conclusions More detailed knowledge of cross-reactivity among ERS components facilitates the interpretation of patch test results and will allow safer ERSs to be composed in the future.

  • an attempt to improve diagnostics of contact allergy due to epoxy resin systems first results of the multicentre study epox 2002
    Contact Dermatitis, 2004
    Co-Authors: Johannes Geier, Holger Lessmann, Uwe Hillen, Uta Jappe, Heinrich Dickel, P Koch, Peter J Frosch, Axel Schnuch, Wolfgang Uter
    Abstract:

    Epoxy resin systems (ERSs) are a frequent cause of occupational allergic contact dermatitis. Sensitization occurs not only to the resins, but also to hardeners and reactive diluents. However, only a fraction of the ERS components currently in use are available for patch testing. With the multicentre study EPOX 2002, we attempted to improve diagnostics in this field by patch testing with components currently used in ERSs. During the first study period (October 2002 to July 2003), in addition to commercially available ERS patch test substances, 16 study substances (1 resin, 9 hardeners and 6 reactive diluents) were patch tested in 70 patients with suspected contact allergy due to ERSs and 22 patients with a prior positive patch test reaction to epoxy resin (ER) in the standard series. Most frequently, allergic reactions to ER based on diGlycidyl Ether of bisphenol A and F were observed (55.2% and 43.7%, respectively). Agreement between positive reactions to both resins, which can be explained by immunological cross-sensitization and/or coexposure, was substantial [Cohen's kappa 0.65 (95% CI: 0.49-0.80)]. Among the reactive diluents, 1,6-hexanediol diGlycidyl Ether (1,6-HDDGE) and 1,4-butanediol diGlycidyl Ether (1,4-BDDGE) were the most frequent allergens, with 19.5% and 18.4% positive reactions, respectively. Although agreement between positive reactions to 1,6-HDDGE and 1,4-BDDGE was even better than with the 2 resins, the sample size is considered too small to decide reliably whEther 1,6-HDDGE alone could serve as a marker allergen for both. Allergic reactions to p-tert-butylPhenyl Glycidyl Ether and to Phenyl Glycidyl Ether (PGE) occurred in 11.5% of the patients tested, with only moderate agreement. All patients positive to cresyl Glycidyl Ether (6.8%) also reacted to PGE. Of the hardeners tested, m-xylylene diamine was the most frequent allergen (13.8%), followed by isophorone diamine (5.7%). No reactions were observed to several substances, the test concentration of which may have been too low and will be increased in the future.