Toxicity, relative sensitivity

The nitrifying organisms are relatively sensitive to many toxic organics, so that the treatment of industrial wastewaters requires special attention to the presence of toxics. 

McCrary JE, Heagler MG. 1997. The use of a simultaneous multiple species acute toxicity test to compare the relative sensitivities of aquatic organisms to mercury. J Environ Sci Health Part A Environ Sci Eng Toxic Hazardous Substance Control 32 73-81. 

This chapter will review some recently completed studies on the long-term effects of MDMA in nonhuman primates. The goals of these studies were to (1) determine if the neurotoxic effects of MDMA, which have been well documented in the rodent (see below), generalize to the primate (2) compare the relative sensitivity of primates and rodents to the neurotoxic effects of MDMA (3) ascertain if the toxic effects of MDMA in the monkey are restricted to nerve fibers (as they are in the rat), or if they involve cell bodies as well (4) evaluate how closely toxic doses of MDMA in the monkey approximate those used by humans and (5) examine whether 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF) can be used to detect MDMA-induced serotonergic damage in the CNS of primates. Before presenting the results of these studies, previous results in the... 

Adverse effects of fenvalerate on survival of terrestrial arthropods were observed at 0.002 to 0.015 pg whole-body topical application, O.llkg/ha aerial application, 5.4 mg/kg in the soil, 50 mg/kg in the diet, and 1.4 g/ant mound (Table 20.4). Synthetic pyrethroids are more effective in biological systems at low temperatures. The relative sensitivity of insects when compared with mammals is attributed in part to this negative temperature coefficient. Thus, warm-blooded animals are less affected than insects and other poikilotherms (Klaassen etal. 1986). Fenvalerate, for example, showed a negative correlation between temperature and toxicity to crickets (Acheta pennsylvanicus), being up to 1.9 times more toxic at 15°C than at 32°C (Harris etal. 1981). A similar case is made for honey bees (Apis mellifera) (Mayer et al. 1987) and for many species of aquatic invertebrates and fish (Mayer 1987). 

Data Adequacy Although human data are limited to primarily occupational monitoring studies, the data base on animal studies is good. The test atmosphere in the key study was supplied via a face mask to the restrained test subjects restrained animals have been shown to be more sensitive than unrestrained animals to inhaled toxicants. Relative species sensitivity to inhaled HCN may be related to breathing rate. Compared to rodents, the slower breathing rate of humans and monkeys may make them less sensitive to the effects of HCN. 

For the purposes of risk assessment the exposed individuals are, in a way, hypothetical, not actual people. By this is meant that they will be assumed to exhibit certain characteristics that make it possible to reach general conclusions regarding the magnitude and duration of their exposure to the chemical of interest, and also their relative sensitivity to its toxic effects. It may be that there are actual people in the population having characteristics closely resembling those assumed by the risk assessor, but it is not possible to know (except in highly unusual circumstances) who those people are. ... 

Hickey, C.W. Martin, M.L. Relative sensitivity of five benthic invertebrate species to reference toxicants and resin acid contaminated sediments. Environ. Toxicol. Chem. 1995, 14, 1401 -1409. 

The experienced reproductive toxicologist understands the normal variability of the various study endpoints, e.g., the prevalence of clusters of cleft palate in the control population of mice. He is also familiar with the relative sensitivity of the various parameters to toxicological insult, e.g., frequent reactive increases in liver weight due to metabolic activation versus the relative stability of brain weight, which is rarely influenced by systemic toxicity. An understanding of the relationship between the endpoints is also important, e.g., an increase in the incidence of morphological abnormalities is more likely to be... 

By far the most comprehensive research into AHR-related effects of PCDD/Fs on fish was a retrospective analysis of Lake Ontario lake trout reproductive impairment due to AHR-mediated early life stage mortality [16]. This includes blue sac disease as well as sublethal effects, which may increase susceptibility of sac fry and alevins to increased mortality and predation during swim-up. Lake trout are more susceptible to AHR-mediated toxic effects than any other Great Lakes species, with the possible exception of mink. WHO TEFs for fish were used to calculate the 2378-TCDD equivalent (TECegg or TEQ) concentrations in lake trout eggs. The validity of the additive toxicity equivalence model was established through early life stage trout toxicity tests. The WHO fish TEFs are likely to be fairly robust for lake trout, since they were determined primarily from relative potency values for effects in embryos of a related salmonid, rainbow trout, even if the relative sensitivity of the species to 2378-TeCDD toxicity may be different. 

Biological activity can be evaluated by using in vitro techniques to determine which effects of the product are related to clinical activity. Due to species specificity of biotechnology derived products, it is necessary to select relevant species for testing. Mammalian cell lines can be used to predict in vivo activity and the relative sensitivity of various species including man. Such studies are useful to determine receptor occupancy, receptor affinity pharmacological aspects, and for the selection of adequate animal species for toxicity testing. 

In mice and rats, sperm motility and count are relatively sensitive and reliable indicators of male reproductive toxicity (Morrissey et al. 1988a,b). Statistically significant, dose-related decreases in these... 

Use individual data points for each experimental concentration (presented as the arithmetic mean standard error of the mean) to construct concentration-response toxicity curves. Such curves are used to calculate midpoint toxicities or NR50 values, as determined by linear regression analysis. Use this value for comparison and ranking against other chemicals, or for relative sensitivity determination of different cell types. 

Considerable species differences in A-esterase activity exist, ranging from very low or nonexistent in certain birds and fish, to very high in rabbits. Species differences in A-esterase activity could account, at least in part, for species differences in the relative sensitivity to certain phosphorothioate insecticides. For example, birds are much more susceptible to the toxicity of pirimiphos methyl than are mammals. 

The relative sensitivity of insects to pyrethrins and pyrethroids is attributable (in roughly equal proportions) to their slower metabolic disposal, to their lower body temperature, and to the inherently higher sensitivity of their target sites. Although there are few, if any, toxic actions of the pyrethroids in insects that do not have their counterpart in man, these three quantitative factors combine to give insect-mammalian toxicity ratios of 2 or 3 orders of magnitude. 

In rats, the LD50 is very low ( 5 mg kg ). Mice and cats are also relatively sensitive to pyriminil toxicity with LD50 values of 98 and 62 mg kg respectively. Other species are markedly less sensitive (LD50 values from 0.5 to 4gkg ). A horse was reported to show... 

There are two basic types of aquatic single-species toxicity tests acute and chronic. Acute toxicity tests have been the workhorse of aquatic toxicologists for many years. These tests are relatively simple, take little time, and are cost-effective. A large historical database exists for many chemicals and effluents. Acute toxicity tests are most often used to quickly screen toxicity or to determine the relative sensitivities of different test species. Mortality is the effect monitored during the test duration of 48 h (invertebrates) or 96 h (fish). In a typical acute toxicity test, 5-10 organisms are exposed under static conditions in glass test beakers to five test concentrations. A control is included. The experiments with test concentrations and control are conducted in triplicate. Daily observations are made on survival, and dead organisms are removed. 

Multiple schedules offer the investigator an opportunity to study behavior controlled by different variables, which may be differentially sensitive to the effects of a toxicant. For example, toluene produced a decrease in test animals response rate in the FR component and an increase in their response rate in the DRL component of a multiple schedule. Furthermore, the relative sensitivity of the two components was different. Similarly, the animals response in the... 

The relative sensitivities to various classes of toxicants of the test species should be known relative to the endpoints to be measured. This criterion is not often realized in environmental toxicology. The invertebrate Daphnia magna is one of the most commonly used organisms in aquatic toxicology, yet only the results for approximately 500 compounds are listed in the published literature. The fathead minnow has been the subject of a concerted test program at the U.S. EPA Environmental Research Laboratory—Duluth, conducted by G. Vieth, yet fewer than a thousand compounds have been examined. In contrast the acute toxicity of over 2000 compounds has been examined using the Norway rat as the test species. 

From the number of different species of fauna (diversity) and an appreciation of their relative sensitivity to pollutants, much can be learned about the condition of fresh or marine waters and sediments [57, 58]. Field experiments to determine the presence or absence of pollution-sensitive species of plants relative to the abundance of tolerant species can also be used [59]. They can also help to determine the bioavailability and acute toxicity of pollutants in bottom sediments. 

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