Aligning chemical assessment tools across the hazard-risk continuum.

With the growing number and diversity of hazard and risk assessment algorithms, models, databases, and frameworks for chemicals and their applications, risk assessors and managers are challenged to select the appropriate tool for a given need or decision. Some decisions require relatively simple tools to evaluate chemical hazards (e.g., toxicity), such as labeling for safe occupational handling and transport of chemicals. Others require assessment tools that provide relative comparisons among chemical properties, such as selecting the optimum chemical for a particular use among a group of candidates. Still other needs warrant full risk characterization, coupling both hazard and exposure considerations. Examples of these include new chemical evaluations for commercialization, evaluations of existing chemicals for novel uses, and assessments of the adequacy of risk management provisions. Even well-validated tools can be inappropriately applied, with consequences as severe as misguided chemical management, compromised credibility of the tool and its developers and users, and squandered resources. This article describes seven discrete categories of tools based on their information content, function, and the type of outputs produced. It proposes a systematic framework to assist users in selecting hazard and risk assessment tools for given applications. This analysis illustrates the importance of careful selection of assessment tools to achieve responsible chemical assessment communication and sound risk management.

Alternatives to animal testing: information resources via the Internet and World Wide Web.

Many countries, including the United States, Canada, European Union member states, and others, require that a comprehensive search for possible alternatives be completed before beginning some or all research involving animals. Completing comprehensive alternatives searches and keeping current with information associated with alternatives to animal testing is a challenge that will be made easier as people throughout the world gain access to the Internet and World Wide Web. Numerous Internet and World Wide Web resources are available to provide guidance and other information on in vitro and other alternatives to animal testing. A comprehensive Web site is Alternatives to Animal Testing on the Web (Altweb), which serves as an online clearinghouse for resources, information, and news about alternatives to animal testing. Examples of other important Web sites include the joint one for the (US) Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and the National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) and the Norwegian Reference Centre for Laboratory Animal Science and Alternatives (The NORINA database). Internet mailing lists and online access to bulletin boards, discussion areas, newsletters, and journals are other ways to access and share information to stay current with alternatives to animal testing.

Human health risk assessment: selected Internet and world wide web resources.

The world wide web (WWW) has become a valuable source of 24 hour-a-day access to information needed by human health risk assessors. Various web sites and other Internet resources provide information needed for human hazard identification, dose-response evaluation, exposure assessment, risk characterization, and risk management. Information on risk communication is also available. Substantial collections of information on multiple aspects of risk assessment are found in sites sponsored by RiskWorld, the (US) EPA's National Center for Environmental Assessment (NCEA), the (US) National Library of Medicine's TOXNET, the (US) Agency for Toxic Substances and Disease Registry (ATSDR), and the International Programme on Chemical Safety (IPCS). Also valuable are various web sites providing information on the physical and chemical properties of chemicals, the environmental fate and transport of chemicals, government regulations, and guidance and training for performing risk assessments. Several professional societies and other organizations have web sites addressing risk assessment issues and information, and there are Internet mailing lists for online help and for sharing information and perspectives. We classify selected web sites according to user needs and provide the reader with a collection of selected sites that can serve as entry points to risk assessment-related web resources.

Global toxicology and risk analysis: roles of the Internet and World Wide Web.

There are many challenges and opportunities in being a global and/or "local" toxicologist, risk assessor, or risk manager. These include the information gathering approaches used to address human hazard identification, exposure assessment, risk characterization, risk management, risk perceptions, and needs for risk communication. Finding the best ways to keep current with the literature and other information associated with the many aspects of toxicology and risk analysis is another challenge and opportunity, as are access to good sources of training and staying aware of the applicable regulations in various countries and regions. Fortunately, a greatly increasing number of people throughout the world will have access to the Internet and World Wide Web; these systems provide 24 h a day access to numerous valuable sources of information and opportunities for training and information sharing.

Longitudinal analysis of the association of human salivary antimicrobial agents with caries increment and cariogenic micro-organisms: a two-year cohort study.

Previous studies of the possible associations of salivary antimicrobial agents with dental caries have given controversial results, obviously mainly because almost all studies have been cross-sectional. Our aim was to find out, in a two-year longitudinal follow-up study, the associations among selected salivary non-immune and immune antimicrobial variables, cariogenic bacteria, and caries increment. The study population was comprised of 63 subjects, all of whom had their 13th birthday during the first study year. In addition to a comprehensive dental examination at baseline and after 2 yrs, paraffin-stimulated whole saliva samples were collected in a standardized way at six-month intervals. Saliva samples were analyzed for flow rate, buffer effect, lysozyme, lactoferrin, total peroxidase activity, hypothiocyanite, thiocyanate, agglutination rate, and total and specific anti-S. mutans IgA and IgG, as well as for numbers of total and mutans streptococci, lactobacilli, and total anaerobic bacteria. Cluster analysis and Spearman-Rank correlation coefficients were used to explore possible associations between and among the studied variables. During the two-year period, a statistically significant increase was observed in flow rate, thiocyanate, agglutination rate, anti-S. mutans IgA antibodies, lactobacilli, and total anaerobes, whereas lysozyme, lactoferrin, and total and anti-S. mutans IgG antibodies declined significantly. Based on various analyses, it can be concluded that, at baseline, total IgG and hypothiocyanite had an inverse relationship with subsequent two-year caries increment, anti-S. mutans IgG antibodies increased with caries development, and mutans streptococci and lactobacilli correlated positively with both baseline caries and caries increment. Total anaerobic microflora was consistently more abundant among caries-free individuals. In spite of the above associations, we conclude that none of the single antimicrobial agents as such has sufficiently strong power to have diagnostic significance in vivo with respect to future caries.

Effects of chlorhexidine-fluoride gel treatments in mothers on the establishment of mutans streptococci in primary teeth and the development of dental caries in children.

In a longitudinal 3-year study, 151 children were followed for the colonization of the primary dentition by mutans streptococci (MS) and for the development of dental caries. At the age of 1 year, the child-mother pairs were divided into three groups on the basis of the levels of MS in maternal saliva. In the experimental group, the mothers had MS levels higher than 10(5) CFU/ml, and they were given chlorhexidine (1%)-sodium fluoride (0.2%) gel treatments twice a year for 3 years. Two control groups were formed. In control group 1, the mothers also had high levels of MS, but no gel was given. In control group 2, the mothers had low (< 10(5) CFU/ml) baseline levels of salivary MS, and no chlorhexidine-fluoride gel was used. In the total study population, 16, 42, and 54% of the children were colonized by MS by the age of 2, 3, and 4 years, respectively. Most children harbored only Streptococcus mutans, but 2 had both S. mutans and Streptococcus sobrinus, and 2 had only S. sobrinus. Twenty-eight percent of the MS-positive children developed caries by the age of 4 years, whereas 4 out of 27 children with dental caries did not have any detectable MS in their plaque samples. Both the colonization by MS and the caries incidence were highest in control group 1 and lower in the experimental group and in control group 2. These observations suggest that the reduction of maternal salivary MS at the time of tooth emergence may delay, or perhaps even prevent, the colonization of MS in the children's primary dentition with a concomitant decline in caries incidence, even in a population with an already low prevalence of dental caries.

Exposure assessment of consumer products: human body weights and total body surface areas to use, and sources of data for specific products.

A thorough understanding of the routes and magnitudes of chemical exposures that consumers experience during the use of a household product is needed as part of a well-founded risk assessment for that product and its components. This review describes some sources of generic consumer data (eg, relevant body weight or total body surface area for a given human age), and exposure-related data (eg, task frequency and duration) for specific product types needed for exposure assessments. The review also contains a discussion of the importance of statistical characterization of the consumer data (eg, does its range follow a normal, log-normal, or other type of distribution?). The importance of examining these data for correlative interactions is emphasized.

Pulmonary toxicity of cyclophosphamide: a 1-year study.

The development of cyclophosphamide-induced pulmonary lesions over a 1-year period was studied in mice. Male BALB/c mice received a single intraperitoneal injection of 100 mg/kg of cyclophosphamide. Within 3 weeks there were scattered foci of intraalveolar foamy macrophages. With time, these foci increased in size and, 1 year later, occupied large areas in all lung lobes. There was also diffuse interstitial fibrosis. Chemical determination done 3, 12, 24, and 52 weeks after cyclophosphamide showed that lungs of animals treated with cyclophosphamide had significantly more hydroxyproline per lung than controls. One year after cyclophosphamide pressure-volume curves measured in vivo were shifted down and to the right and total lung volumes were decreased. A single injection of cyclophosphamide produced an irreversible and progressive pulmonary lesion.

The role of toxicological interactions in lung injury.

Interactions between two or more toxic agents can produce lung damage by chemical-chemical interactions, chemical-receptor interactions or by modification, by a first agent, of the cell and tissue response to a second agent. Interactions may occur by simultaneous exposure and if exposure to the two agents is separated in time. Chemical-chemical interactions have been mostly studied in the toxicology of air pollutants, where it was shown that the untoward effect of certain oxidants may be enhanced in the presence of other aerosols. Interactions at the receptor site have been found in isolated perfused lung experiments. Oxygen tolerance may be an example, when pre-exposure to one concentration of oxygen mitigates later exposure to 100% oxygen by modifying cellular and enzymatic composition of the lung. Damage of the alveolar zone by the antioxidant butylated hydroxytoluene (BHT) can be greatly enhanced by subsequent exposure to oxygen concentration which, otherwise, would have little if any demonstrable effect. The synergistic interaction between BHT and oxygen results in a resulting interstitial pulmonary fibrosis. Acute or chronic lung disease may then be caused not only by one agent, but very likely in many instances by the interaction of several agents.

Acute inhalation toxicity of 3-methylfuran in the mouse: pathology, cell kinetics, and respiratory rate effects.

The acute inhalation toxicity of 3-methylfuran (3MF) was investigated in male BALB/c mice by morphologic examination of animals killed at varying timepoints following a 1-hr exposure to an initial chamber concentration of 14 to 37 mumol/liter (343 to 906 ppm). In addition, respiratory rate measurements and cell kinetics were used to assess quantitatively pulmonary damage and repair. Necrosis of nonciliated bronchiolar epithelial (Clara) cells was seen 1 day following exposure and was followed by regeneration, which was virtually complete, within 21 days. Cell kinetic studies showed peak bronchiolar cell proliferation at 3 days with a labeling index (LI) of 5.0% compared to 0.4% in controls. An increase in parenchymal cell proliferation was also noted coincident with a mild interstitial pneumonitis. This parenchymal proliferation, peaking at 10 days with an LI of 1.4% compared to 0.2% in controls, consisted primarily of type II epithelial and endothelial cell proliferation indicating possible delayed damage and repair of type I epithelial and endothelial cells. The respiratory rate showed an initial transient increase followed by a more prolonged decrease with eventual return to control levels. 3MF toxicity was also evidenced by a necrotizing suppurative rhinitis, centrilobular hepatic necrosis, lymphocyte necrosis in the thymus and spleen, sialoadenitis, and otitis media.

Pathology of acute inhalation exposure to 3-methylfuran in the rat and hamster.

The acute inhalation toxicity of 3-methylfuran (3MF) was investigated in SPF Fischer-derived and CD/CR rats, and golden Syrian hamsters by determination of the 2-week LC50, and by histologic examination of animals killed 1, 3, and 14 days following a 1-hr exposure to 148 and 322 mumole 3MF/liter for CD/CR rats and hamsters, respectively. The Fischer-derived rat was more sensitive to 3MF-induced lethality than the CD/CR rat with an LC50 in the male rat of 81 mumole/liter-1 hr as compared to 222 mumole/liter-1 hr. No sex difference was found. The hamster was relatively resistant with no lethality at 322 mumole 3MF/liter-2 hr. Pulmonary damage was present in both species. In the hamster, selective necrosis of nonciliated bronchiolar epithelial (Clara) cells was seen at 1 day with virtually complete regeneration by 14 days whereas in the rat the bronchiolar epithelial damage was more extensive and was followed by scattered peribronchiolar fibrosis and epithelial mucous metaplasia suggestive of "small airway disease" of man. Relatively selective 3MF-induced necrosis of olfactory epithelium occurred in the nasal mucosa of both species. Resolution of this lesion was seen by 14 days in the hamster. In the rat, however, the necrosis was much more extensive and was followed by partially occlusive fibrosis of the nasal cavity as seen at 14 days. 3MF also induced centrilobular hepatic necrosis in both species. In the rat, lymphocyte necrosis in the thymus and spleen, and esophageal necrosis was also seen.

Potentiation of butylated-hydroxytoluene-induced acute lung damage by oxygen. Effects of prednisolone and indomethacin.

We have previously shown that administration of the antioxidant butylated hydroxytoluene (BHT) to mice produces lung damage that can be markedly potentiated by hyperoxia resulting in pulmonary fibrosis. In the present studies using this model, we show that: (1) in animals treated with BHT-O2, prednisolone given for 12 successive days does prevent excessive collagen accumulation provided lung collagen is measured immediately after terminating steroid therapy, whereas a rebound effect occurs later on; (2) limitation of steroid treatment to the first 6 days after acute lung injury enhances accumulation of collagen, whereas steroids given later, on Days 7 through 12, have an alleviating effect; (3) indomethacin under the conditions described is not an effective treatment.

Effect of lung, liver, and kidney toxicants on respiratory rate in the mouse.

The intraperitoneal administration of either butylated hydroxytoluene (BHT) +/- thoracic X-irradiation, or cyclophosphamide, and intravenous injection of oleic acid, resulted in lung injury and repair in BALB/c mice which could be assessed in unanesthetized animals by changes in respiratory rate (RR) using a total body plethysmograph. Studies with BHT +/- X-rays, and cyclophosphamide found that the RR right before sacrifice (2 weeks after BHT and 3 weeks after cyclophosphamide) correlated well (r = 0.19) with the degree of pulmonary fibrosis as measured by changes in hydroxyproline content. However, prior to this timepoint, there was a peak and trough in respiratory rate response that could not be correlated with the time course of fibrosis development in the BHT-X-ray model. In an effort to determine the influence of pulmonary edema and lung cell proliferation on respiratory rate changes, an agent (oleic acid) capable of producing lung injury followed by a high level of cellular proliferation with only minimal development of fibrosis was studied. These studies showed that good correlations were found on day 3 following injection (day of peak increase in respiratory rate) between respiratory rate and either lung wet weight (r = 0.81) or the degree of cellular proliferation as measured by the incorporation of thymidine into pulmonary DNA (r = 0.80). Liver (carbon tetrachloride) and kidney (mercuric chloride) toxicants, and starvation produced decreases or no change in RR.

Potentiating effects of oxygen in lungs damaged by methylcyclopentadienyl manganese tricarbonyl, cadmium chloride, oleic acid, and antitumor drugs.

The intraperitoneal administration of methylcyclopentadienyl manganese tricarbonyl (MMT) and cyclophosphamide, exposure to an aerosol of cadmium chloride, intravenous administration of oleic acid, and intratracheal instillation of bleomycin to young female BALB/c mice or CD/CR rats result in acute lung injury. Pulmonary morphology and lung collagen content were examined in animals treated with these chemicals alone or in combination with an elevated oxygen concentration (80%) in the inspired air. In mice, the development of fibrosis could be significantly enhanced if animals treated with MMT, cadmium chloride, cyclophosphamide, or bleomycin were exposed to 80% oxygen immediately following exposure to these agents. In rats only cyclophosphamide- and bleomycin-induced acute lung injury was potentiated by hyperoxia, resulting in significant enhancement of lung collagen content. The pathogenesis responsible for this differential species response of pulmonary injury to hyperoxia remains to be investigated.

Nonciliated bronchiolar epithelial (Clara) cell necrosis induced by organometallic carbonyl compounds.

The administration of transition metal organometallic compounds such as manganese, chromium, and iron carbonyls by the i.p. route, and nickel by inhalation (mice) or intravenously (rats), resulted in selective necrosis of the nonciliated bronchiolar epithelial (Clara) cells and variable pulmonary parenchymal damage in BALB/c mice and Fischer-derived rats within 24 h of administration. The pulmonary toxicity of methylcyclopentadienyl manganese tricarbonyl (MMT), a representative of this group of compounds, was enhanced by pretreatment with piperonyl butoxide (PB), an inhibitor of the mixed-function oxidase system. This finding suggests that Clara cell necrosis can result from direct toxicity and that the specificity of toxic agents for Clara cells may not be related solely to the presence of the mixed-function oxidase system.

Hyperoxia, but not thoracic X-irradiation, potentiates bleomycin- and cyclophosphamide-induced lung damage in mice.

The intraperitoneal administration of cyclophosphamide or bleomycin to BALB/c mice resulted in lung cell damage followed by cellular proliferation, which was quantitated by measuring the increase in thymidine incorporation into pulmonary DNA. We have previously shown that administration of the antioxidant butylated hydroxytoluene produces lung damage that can be potentiated by both hyperoxia and thoracic X-irradiation. In the present study we show that hyperoxic exposure also potentiates bleomycin- and cyclophosphamide-induced acute lung damage. However, thoracic X-irradiation does not potentiate bleomycin- and cyclophosphamide-induced lung toxicity.

Modification of lung tumor development in A/J mice.

Strain A mice were injected with urethan, 3-methylcholanthrene or dimethylnitrosamine and given repeated injections of butylated hydroxytoluene (BHT). This treatment significantly increased multiplicity of lung tumors induced by all 3 carcinogens. Two other antioxidants, butylated hydroxyanisole (BHA) or alpha-tocopherol (vitamin E) did not enhance tumor formation, nor did methylcyclopentadienyl manganese tricarbonyl (MMT), an agent capable of producing cell proliferation in lung. Lungs were more susceptible to the carcinogenic action of urethan 2 weeks following BHT-induced injury, but not during the phase of acute cell proliferation in lung. It is concluded that the effects of BHT on lung tumor development in mice are not related to its properties as an antioxidant or to its capability to produce extensive cell proliferation in lung.