The use of in vitro methods for hazard characterisation of chemicals

Mass dose rates of particle-bound organic pollutants in the human respiratory tract: Implications for inhalation exposure and risk estimations

To date, little is known about the effective doses of airborne particulate matter (PM) and PM-bound hazardous organic components to the human respiratory tract (HRT). In the light of this, here we provide particle mass dose rates (dose per hour of exposure) of PM and a suite of PM-bound hazardous organic compounds in the HRT for two population age groups (adults & children). More specifically, the mass dose rates of PM and PM-bound polycyclic aromatic hydrocarbons (PAHs), nitrated-PAH (NPAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) were estimated at two urban sites using a multiple path particle dosimetry model. We find that, in most cases, the total mass doses are following similar variations across sites and seasons as their ambient total concentrations, however their distribution in the HRT is a function of the particle size distributions and the physiological parameters of each age group. More specifically, the majority of the deposited mass of PM and all the chemical components investigated was accumulated in the upper airways instead of the lungs. We further show that children, due to their different physiology, are more susceptible and receive larger fraction of the total mass doses in the deepest parts of the lungs compared to the adults' group. Comparing the traditional method for estimating the inhalation risk, which is based on the ambient concentration of pollutants, and a modified version using the mass dose in the HRT, we find that the former may overestimate the reported risks. The results presented here provide a novel dataset composed by previously undetermined doses of hazardous airborne particulate organic components in the HRT and demonstrate that alternative health risk estimation approaches may capture some variabilities that are traditionally overlooked.

A computational model to predict rat ovarian steroid secretion from in vitro experiments with endocrine disruptors

A finely tuned balance between estrogens and androgens controls reproductive functions, and the last step of steroidogenesis plays a key role in maintaining that balance. Environmental toxicants are a serious health concern, and numerous studies have been devoted to studying the effects of endocrine disrupting chemicals (EDCs). The effects of EDCs on steroidogenic enzymes may influence steroid secretion and thus lead to reproductive toxicity. To predict hormonal balance disruption on the basis of data on aromatase activity and mRNA level modulation obtained in vitro on granulosa cells, we developed a mathematical model for the last gonadal steps of the sex steroid synthesis pathway. The model can simulate the ovarian synthesis and secretion of estrone, estradiol, androstenedione, and testosterone, and their response to endocrine disruption. The model is able to predict ovarian sex steroid concentrations under normal estrous cycle in female rat, and ovarian estradiol concentrations in adult female rats exposed to atrazine, bisphenol A, metabolites of methoxychlor or vinclozolin, and letrozole.

Characterization of cytotoxicity of airborne particulates from urban areas of Lahore

A number of species (organic and inorganic) in airborne particulates cause the toxicity to living being. The potential of in vitro test methods were explored for toxicity assessment of trace toxic elements (inorganic species) present in ambient air on human being (lungs). A year long sampling of airborne particles (PM2.5) was carried (April 2008 to March 2009) in Lahore, Pakistan. A total of thirty nine samples were collected on 47 mm Zefluor Teflon filter membranes and each was analysed to characterize for the elements: Sb, As, Be, Cd, Cr, Co, Pb, Mn, Hg using ICP-MS in water extract and total acid digestate. The samples cytotoxicity was also established using lung derived cells and MTS colorimetric assays. This generated dose response curves and IC50 values for the elemental mixtures identified on the Teflon filter membrane. The results indicated that even at low concentrations airborne elemental mixtures displayed an additive toxic effect.

Toxicity Assessment of Industrial Chemicals and Airborne Contaminants: Transition fromIn VivotoIn VitroTest Methods: A Review

Exposure to occupational and environmental contaminants is a major contributor to human health problems. Inhalation of gases, vapors, aerosols, and mixtures of these can cause a wide range of adverse health effects, ranging from simple irritation to systemic diseases. Despite significant achievements in the risk assessment of chemicals, the toxicological database, particularly for industrial chemicals, remains limited. Considering there are approximately 80,000 chemicals in commerce, and an extremely large number of chemical mixtures, in vivo testing of this large number is unachievable from both economical and practical perspectives. While in vitro methods are capable of rapidly providing toxicity information, regulatory agencies in general are still cautious about the replacement of whole-animal methods with new in vitro techniques. Although studying the toxic effects of inhaled chemicals is a complex subject, recent studies demonstrate that in vitro methods may have significant potential for assessing the toxicity of airborne contaminants. In this review, current toxicity test methods for risk evaluation of industrial chemicals and airborne contaminants are presented. To evaluate the potential applications of in vitro methods for studying respiratory toxicity, more recent models developed for toxicity testing of airborne contaminants are discussed.

Use of the dog as non-rodent test species in the safety testing schedule associated with the registration of crop and plant protection products (pesticides): present status

The results from a survey of the expert information that is publicly accessible on the use of the dog as test species during the regulatory evaluation of agricultural chemicals and pesticides are reported. Methods that are being used or considered in order to reduce the number of dogs used for this purpose are described. Regulatory evaluation aims at establishing threshold values for safe human exposure; it is based on no-observed-adverse-effect levels (NOELs) determined in animal studies. Current regulations require testing in two species, a rodent species (usually rat or mouse), and a non-rodent species (usually the dog). Subchronic (90-day) and chronic (12-month) repeated-dose feeding studies must be routinely conducted in dogs. This report first focuses on the results from a retrospective study analysing data on 216 pesticides kept on record by the Bundesinstitut für Risikobewertung, BfR (German Federal Institute for Risk Assessment), the competent regulatory authority in Germany. The study was sponsored and coordinated by SET, the German Foundation for the Promotion of Research on Replacement and Complementary Methods to Reduce Animal Testing (Stiftung zur Förderung der Erforschung von Ersatz-und Ergänzungsmethoden zur Einschränkung von Tierversuchen, Mainz) and conducted by the BfR. Since the data submitted for registration of a product is the property of the manufacturer, the study could only proceed with the collaboration of the German Association of Manufacturers of Agricultural Chemicals (Industrieverband Agrar, IVA). To ensure confidentiality, designated codes were used instead of the compounds' proper names when the study was published. The results support two major conclusions. The use of the dog for the testing of pesticides is indeed necessary because the dog has proved to be the most sensitive species for about 15% of the compounds examined. However, chronic studies are only of limited value since they only provide essential information that cannot be obtained in sub-chronic studies in about 5% of cases. These conclusions are supported by several retrospective analyses using data on pharmaceutical drugs carried out in the context of the International Conference on Harmonisation of Technical Requirements for the Registration of Pharmaceuticals for Human Use (ICH). Over 90% of drugs elicited no toxic symptoms in 12-month studies in dogs in addition to those that had been recorded previously in studies conducted for 90 or 180 days in dogs and rats. Another approach comparing the results from pre-clinical animal studies with clinical studies noted that animal studies predicted about 70% of the effects observed in volunteers, and in about 94% of cases the effects occurred in animal studies lasting not more than one month. Furthermore, the report summarises the current methods under consideration that could refine or reduce the use of dogs in toxicity testing: industrial data sharing and harmonisation of guidelines, in vitro methods, human studies, computational prediction models, and integrated testing approaches. The integrated Agricultural Chemicals Safety Assessment (ACSA) testing scheme, which is currently being developed in an international project initiated by the International Life Sciences Institute (ILSI, USA), is of particular relevance, since an ambitious attempt is being made to design a new comprehensive test framework incorporating modern scientific approaches and covering most aspects of current regulatory testing requirements. The ACSA project has access to the pesticide database of the US EPA's Office of Pesticide Programs (OPP). Preliminary results have confirmed the two major conclusions from the joint SET/BfR study conducted in Germany. Taking these results into account, it is recommended that the regulatory requirement for 12-month studies to be routinely carried out in dogs should be abandoned. While 90-day studies should be conducted in both rats and dogs, chronic studies should only take place in rats. If the dog is more sensitive than the rat in the 90-day study, an additional safety factor to the NOEL value obtained in the chronic rat study should be applied in order to set the threshold for safe human exposure, instead of conducting a 12-month study in dogs. This safety factor may be calculated from chronic NOEL data available in several pesticide databases. Chronic tests using dogs would then only be required if the test compound belongs to a new class of chemicals that has never been tested before. Thus, the report concludes that, according to current scientific knowledge, the routine 12-month studies in dogs are no longer required for agricultural chemicals and pesticides, and international regulations should be changed accordingly. Active international support of such measures is welcomed, from both an economical and an animal welfare perspective.

Ebselen and diphenyl diselenide change biochemical hepatic responses to overdosage with paracetamol

The toxicity of paracetamol is largely related to its conversion to the reactive intermediate alkylating metabolite N-acetyl-para-benzo-quinoneimine (NAPQI). δ-Aminolevulinate dehydratase (δ-ALA-D) is a sulfhydril containing enzyme which is extremely sensitive to oxidizing and alkylating agents. In the present study, we examined whether acute treatment with paracetamol changes δ-ALA-D activity. The influence of two organochalcogenides with glutathione peroxidase-like activity, diphenyl diselenide [(PhSe)(2)] and ebselen was also assessed as potential protecting agents against paracetamol toxicity. Paracetamol (1200mg/kg for three days 4h after the injection of DMSO, diphenyl diselenide (100μmol/kg) or ebselen (100μmol/kg) caused an inhibition of about 40% (P < 0.01) in hepatic δ-ALA-D. Ebselen restored enzyme activity to control values. Non-protein-SH and ascorbic acid were diminished to 50% of control value by paracetamol, independent of chalcogenides treatment (all P values <0.05). In view of the fact that paracetamol caused a massive reduction in non-protein-SH and ascorbic acid, we realize that the protective effect of ebselen on δ-ALA-D activity is mediated by its thiol peroxidase-like activity or by a direct interaction with NAPQI and other reactive species formed during paracetamol metabolism.

Molecular targets of lead in brain neurotoxicity

The detrimental effects of lead poisoning have been well known since ancient times, but some of the most severe consequences of exposure to this metal have only been described recently. Lead [Pb(II)] affects the higher functions of the central nervous system and undermines brain growth, preventing the correct development of cognitive and behavioral functions. As an established neurotoxin, Pb(II) crosses the blood-brain barrier rapidly and concentrates in the brain. The mechanisms of lead neurotoxicity are complex and still not fully understood, but recent findings recognized that both Ca(II) dependent proteins and neurotransmitters receptors represent significant targets for Pb(II). In particular, acute and chronic exposure to lead would predominantly affect two specific protein complexes: protein kinase C and the N-methyl-D-aspartate subtype of glutamate receptor. These protein complexes are deeply involved in learning and cognitive functions and are also thought to interact significantly with each other to mediate these functions. This review outlines the most recent hypotheses and evidences that link lead poisoning to impairment of these protein functions, as well as the in vitro experimental approaches that are most likely to provide information on basic mechanicistic processes.

The ECVAM workshops: a critical assessment of their impact on the development, validation and acceptance of alternative methods

ECVAM initiated its workshop programme in 1994, to enable it to become well informed about the state of the art of non-animal test development and validation, and about the possible incorporation of alternatives into regulatory requirements for safety testing. Fifty-one such workshops have been held on specific topics, up to 2002. In these workshops, the current status of in vitro tests and their potential uses were reviewed and recommendations were made as to the best ways forward to progress and enhance the utilisation of in vitro methods. Reports for 46 of these workshops have been published in ATLA. Most of the workshops focused on in vitro replacement methods, although an increasing number have dealt with reduction and refinement. The recommendations in the ECVAM workshops have been progressed further by: a) the formation of ECVAM task forces; b) the organisation of further workshops; c) the activities of scientific committees; d) the provision of earmarked research funding; and e) the conduct of validation studies. Examples of each of these activities are discussed. Some individual workshops are covered in more detail and several recommendations that have so far not been acted on are also considered. The workshops and their reports have had a substantial effect on the development and implementation of alternative methods, and have been a major factor in contributing to the success of the first nine years of ECVAM's existence. It is strongly recommended that ECVAM continues to organise workshops and to publish their findings, and several suggestions are made for topics of future workshops.