ABSTRACT
Due to its endocrine disruptive activity, the plastic additive Bisphenol A (BPA) is classified as substance of very high concern (EU ECHA 2017). A correlation between environmental exposure to BPA and congenital defects has been described in humans and in experimental species including the amphibian Xenopus laevis, where severe branchial defects were associated to lethality. The exposure of X. laevis embryos to the BPA analogue bisphenol B (BPB) was recently linked to similar teratogenic effects, with BPB having relative potency about 3 times higher than BPA. The combined BPA-BPB exposure is realistic as both BPA and BPB are detected in human samples and environment. Limited experimental data are available on the combined developmental toxicity of BPA and BPB. The aim of the present work is to evaluate the effects of BPA and BPB mixture in the X. laevis development model, using R-FETAX procedure. The exposure was limited to the first day of development (corresponding to the phylotypic developmental period, common to all vertebrates). Samples were monitored for lethal effects during the full six-day test period and the external morphology was evaluated at the end of the test. Mixture effects were described by modelling, using the PROAST software package. Overall data modelling showed that dose-addiction could not be rejected, suggesting a health concern for co-exposure.
ABSTRACT
Bisphenol A (BPA) is a plastic additive with endocrine disruptive activity, classified in 2017 by EU ECHA as substance of very high concern. A correlation between environmental exposure to BPA and congenital defects has been described in humans and in experimental species, including the amphibian Xenopus laevis. Among BPA analogues, bisphenol B (BPB) is used as alternative in different not-EU countries, including US, but seems to share with BPA its endocrine disruptor properties. Aim of the present work is the evaluation of the effects of BPB versus BPA exposure in a X. laevis developmental model. A windowed exposure (R-FETAX method) was applied covering the developmental phylotypic period (teratogenicity window), or the late tailbud stages (neuro-behavioural toxicity window, corresponding to the spontaneous swimming acquisition period). Samples were monitored for lethal effects during the full test period. External morphology evaluation and deglutition functional test were applied in any group. Abnormal tadpoles were also processed for cartilage staining. In groups exposed during neuro-behavioural toxicity window the swimming test was also applied. Lethality and malformations were obtained only in samples exposed during the teratogenicity window; these data were modelled using PROAST software and BPB relative potency resulted about 3 times higher than BPA. The day-by-day evaluation revealed that lethality was correlated to embryonic abnormal development of gills and apoptosis in gill primordia. Teratogenicity was never detected in groups exposed during the neuro-behavioural toxicity window, where some significant neuro-behavioural deficits were detected in tadpoles exposed to the highest tested concentrations of BPA and BPB.
Subject(s)
Phenols , Teratogens , Humans , Animals , Teratogens/toxicity , Xenopus laevis/abnormalities , Phenols/toxicity , Benzhydryl Compounds/toxicityABSTRACT
The evaluation of chemical risk in agriculture is complicated because of difficulties in obtaining measures representative of working conditions. This is the reason why experiences finalized at producing risk estimates are running. In this frame, a Regional working group has developed the project "Pesticide exposure and risk profiles in agriculture". Priority scenarios have been selected and the main variables correlated with pesticide exposure have been pointed out. A value for each variable has been defined. The sum of these values allows the definition of "Exposure Indices" (EI), which can be reduced by multiplication for a coefficient calculated based on use of personal protective devices, training and education and equipment conditions. A Risk Index is calculated as the product of EI per a toxicity index, calculated based on the risk phrases of the substances used ("Risk Profile"). Risk Profiles allow the production of risk estimates and the definition of the appropriate preventive interventions. Next phase will be addressed at the validation of the model, to be carried out through the determination of the levels of concordance between the risk class allocation obtained from the model and the one obtained from environmental and biological measures, in the same groups of workers.
