The INDEX Project - Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU

The INDEX project (Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU), coordinated by the EU/JRC and funded by DG SANCO, has been finished in December 2004. The project was carried out in collaboration with a Steering Committee of leading European experts in the area of indoor air pollution. Scope of INDEX was to identify priorities and to assess the needs for a Community strategy and action plan in the area of indoor air pollution. The key issues that have been addressed within the project are: - the setting up of a list of compounds to be measured and regulated in indoor environments with priority, on the basis of health impact criteria - to provide suggestions and recommendations on potential exposure limits for these compounds and - to provide information on links with existing knowledge, ongoing studies, legislation etc. at world scale. Suggestions and recommendations on potential exposure limits or other exposure control actions were defined for five prioritised compounds; formaldehyde, nitrogen dioxide, carbon monoxide, benzene, and naphthalene.JRC.I.5-Physical and chemical exposure

Chemical-induced allergy and autoimmunity

This thesis aims towards a better understanding of the mechanisms that lead to chemical-induced adverse immune effects. We focussed thereby on the initial induction stage of the immune reaction that consists of three major steps: (i) formation of neoantigen, (ii) processing and presentation of the neoantigen, and (iii) recognition of peptide-MHC-complex by the T cell. Chemical induced allergy or autoimmunity is often observed after administration of certain drugs or after contact with industrial or environmental chemicals. T cells play a central role in the development of drug-induced adverse immune reactions. A major difficulty in studying T-cell reactions to sensitizing chemicals is the fact that in most cases the ultimate neoantigen recognized by "drug-specific" T cells is unknown. As most T cells can only recognize peptides on MHC molecules, chemicals have to bind to a protein carrier in order to be recognized by T cells. Parts of this neoantigen are presented on MHC molecules on the surface of the APC and can be engaged by T cells. In order to bind to proteins, most chemicals have to be metabolized into protein-reactive intermediates, called haptens. Although the liver is the main organ for metabolic transformation, it does not play a major role in the induction of chemical induced adverse immune effects. In contrast, cells from the immune system itself, like neutrophils and monocytes have been shown to be involved in drug-metabolism prior to drug-induced adverse immune effects. In this thesis we have tried to elucidate some of the mechanisms involved in chemical induced adverse immune effects. Some of the steps possibly involved in the formation of neoantigens and subsequent T cell recognition are discussed. The hypothesis that extrahepatic metabolism plays an important role in the formation of neoantigen with the prohaptens procainamide and aniline could be substantiated, and the processing of protein adducts, presentation of neoantigens and subsequent recognition of either haptenated peptides or cryptic peptides by T cells was shown. Furthermore, this thesis elucidates some of the mechanisms involved in cross-sensitization and discusses the possible implications of T-cell cross-reactivity in chemical induced allergy and autoimmunity

Immunotoxicity of the pyrrolizidine alkaloid monocrotaline in C57B1/6 mice

Monocrotaline (MCT) is a member of a class of naturally occurring phytotoxins known as pyrrolizidine alkaloids (PAs). Exposure to PAs can result in liver and cardiopulmonary lesions as well as lymphoid organ atrophy. In the present study C57BI/6 (B6) mice received MCT (0-150 mg/kg/day, po) for 14 days. Overt toxicity was minimal and observed only at highly immunosuppressive doses. Following MCT exposure, significant dose-dependent suppressions were observed in the following immune responses: numbers of antibody producing cells, cytotoxic T- lymphocyte activity, and NK cell cytotoxicity. The antibody responses to the T cell-dependent antigen, SRBC, and the T cell-independent (TI) antigens, DNP-Ficoll and TNP-LPS, were decreased with identical dose response curves. This, along with data showing MCT decreased blastogenesis of B cells more than T cells at the lowest dose level, and that high doses induced significant decreases in the total number of B cells only, suggest that the B cell may be more sensitive than T cells, NK cells , or macrophages. The liver and lung toxicity of MCT is believed to be mediated through its metabolism by mixed function oxidase (MFO) enzymes to reactive pyrroles (monocrotaline pyrrole, MCTP; and dihydropyrrolizine, DHP). Accordingly, it was our hypothesis that the immunotoxicity could be modulated by altering MFO activity. To test this, mice were given a single dose of MCT (100 or 200 mg/kg, po) after MFO induction with phenobarbital; in other experiments mice received the MFO inhibitor chloramphenicol immediately before and 3 hrs after a single exposure to MCT (300 mg/kg, po). However, neither MFO induction nor inhibition significantly altered the immunosuppressive potency of MCT. The antibody and blastogenic responses of splenic lymphocytes directly exposed to MCT (1-3 mM) or MCTP (1-8 μM) in culture were inhibited in a concentration-dependent manner, indicating that both parent and metabolite were immunotoxic. However, the inability to alter the in vivo immunotoxicity by altering MFO activity questions the role this metabolite may play in vivo. In conclusion, the immune system in B6 mice is a sensitive target of MCT toxicity. Inhibition of blastogenesis appears to be one mechanism of MCT-induced immunosuppression. In contrast to other toxic effects of MCT, our results suggest that the parent compound itself plays a significant role in the immunotoxicity

The Immunological and Neurochemical Toxicity of Benzene and its Interaction with Toluene in Mice

Benzene and toluene are known groundwater contaminants . Male CD-I mice were continuously exposed to 0, 31, 166, and 790 mg/ L benzene and 0, 17, 80, and 405 mg/L toluene, respectively, in drinking water for four weeks. Benzene caused a reduction of leukocytes, lymphocytes and erythrocytes, and resulted in a macrocytic anemia. Lymphocyte response to both B- and T-cell mitogens, mixed lymphocyte response to alloantigens, and the ability of cytotoxic lymphocytes to lyse tumor cells were enhanced at the lowest dose of benzene and depressed in the higher dosage animals. Benzene at doses of 166 and 790 mg/L decreased the number of sheep red blood cell (SRBC) -specific plaque-forming cells, the level of serum anti-SRBC antibody, and the activity of interleukin-2 (IL -2). Benzene treatment increased endogenous concentrations of the brain biogenic amines norepinephrine (NE), dopamine (DA) and serotonin (5-HT), and concomitantly, elevated the levels of their respective major metabolites vanillymandelic acid (VMA), 3,4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), in several brain regions . In most cases, the changes were dose related; in several instances, maximum effects occurred at the 166 mg/L benzene dose. Toluene did not adversely affect the hematological parameters. Depression of immune function was evident at the highest dose (405 mg/L), except for mitogeneses. Increased neurochemical concentrations caused by toluene displayed a dose-dependent biphasic manner which began at a dose of 17 mg/L, peaked at 80 mg/L, and decreased at 405 mg/L. Toluene treatment had more selective effects on NE, 5-HT ,VMA and 5-HIAA, than DA, DOPAC and HVA. Both compounds, by increasing concentrations of the hypothalamic NE and its major metabolite VMA, stimulated the hypothalamic-pituitary-adrenocortical axis activity, resulting in an elevated plasma adrenocorticotropic hormone and serum corticosterone which had an additive adverse effect on IL-2 synthesis. Toluene, 325 mg/ L, completely inhibited benzene-induced cytopenia and immunosuppression when it was coadministered with benzene (166 mg/L). The low dose of toluene (80 mg/L ) did not antagonize benzene immunotoxicity. Mice given the combined exposures exhibited raised levels of regional neurochemicals when compared to the untreated controls. Increased levels of monoamine metabolites in several brain regions were greater in the combined treatments of benzene and toluene than when either chemical was used alone. The results of the interaction studies support the known metabolic interaction mechanisms of benzene and toluene

Toxicological profile for nitrobenzene : draft for public comment : April 2022

VERSION HISTORYDate DescriptionApril 2022 Draft for public comment toxicological profile releasedDecember 1990 Final toxicological profile releasedtp132.pdf20221138

Studies on molecular mechanisms of the immunotoxic effects of propanil on T cell development and cytokine production.

Propanil is a post-emergent herbicide which has been extensively used for control of weeds in rice and wheat field. Acute exposure to propanil central nervous system depression, loss of a righting reflex, and cyanosis. The immunotoxic effects of propanil on animals include reduction of thymus weight and cellularity with increase of spleen weight and cellularity, inhibition of humoral and cell-mediated immune response and alteration NK cell activity and macrophage cytotoxicity. The overall goal of this project is to investigate the mechanism and recovery of propanil induced thymic atrophy and the effect of propanil on T cell cytokine production. Using cell surface staining with flow cytometry, we found that the thymic atrophy was characterized by a depletion of CD4{dollar}\\rm\\sp+CD8\\sp+{dollar} population. No atrophy was observed in adrenalectomized, propanil-treated mice, suggesting that the immunotoxic effect of propanil on thymus appears to be mediated, in part, by endogenous glucocorticoids. DNA staining data showed higher percentage of proliferating CD4{dollar}\\rm\\sp+CD8\\sp+{dollar} thymocytes 4 days after exposure. Thus, recovery of the thymus occurs following increases in thymocyte proliferation, most notably the immature CD4{dollar}\\rm\\sp+CD8\\sp+{dollar} thymocytes. We used both in vivo and in vitro models to study the effect of propanil on T cell cytokine production. In vivo exposure to propanil selectively inhibits the production of IL-2, 6, GM-CSF, and IFN-{dollar}\\gamma.{dollar} In vitro exposure model demonstrated that splenocytes produce significant less IL-2, IL-6, IFN-{dollar}\\gamma{dollar} and GM-CSF after propanil treatment. We then used a T cell line, EL-4 cells to further investigate the mechanism of propanil caused inhibition of IL-2 production at protein, message and gene expression levels. Quantitave Northern blot analysis of IL-2 mRNA showed a dose-dependent decrease in propanil treated EL-4 cells upon PMA stimulation. To determine if the reduced message production was due to reduced signaling or message stability, nuclear run-on and mRNA stability assays were performed. Nuclear run on assays revealed that the transcription rate of the IL-2 gene was decreased by approximately 50% in the presence of 0.02 mM propanil. IL-2 message stability assays also revealed a reduction in message stability. Taken together, these results suggest that propanil inhibits IL-2 production at both transcriptional and post-transcriptional levels