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The Toxic Environment and Its Medical Implications with Special Emphasis on Smoke Inhalation
Published in Jacob Loke, Pathophysiology and Treatment of Inhalation Injuries, 2020
Jacob Loke, Richard A. Matthay, G. J. Walker. Smith
In a study of wood and upholstery fires in a nonventilated room, the maximum carbon monoxide concentration (recorded by a portable carbon monoxide sampler) was 12,000 parts per million (ppm) (Sidor et al, 1973). In a fire situation, there may be a wide range of carbon monoxide concentrations in the ambient air depending on the amount of air supply and ventilation. Poorly ventilated, closed space buildings can have carbon monoxide levels of 3000 ppm (Barnard and Weber, 1979) (Table 4). In experimental fire studies of aircraft interiors to simulate postcrash fires, 90 seconds after ignition of the full-scale fire test, carbon monoxide concentration reached 10,000 ppm in the cabin; in another test, the carbon monoxide levels attained 26,000 ppm in 180 seconds (a fatal level for a 2.5 min exposure) (Mohler, 1975). In a study of the fire environments in the Dallas area, only 10.5% of the fires had carbon monoxide levels that exceeded immediate danger to life or health (1500 ppm) and the short-term lethal concentration (5000 ppm) (Table 2). Firefighters as well as fire victims can be exposed to lethal carbon monoxide levels in fires. For this reason, and due to the presence of other toxic gases in a fire, firefighters should always wear a compressed air breathing apparatus during fire fighting and rescue operations. It has been shown that wearing this apparatus results in a reduced blood carboxyhemoglobin levels after fires (Radford and Levine, 1976; Loke et al., 1976).
Obstruction of the Respiratory Orifices, Larynx, Trachea and Bronchia
Published in Burkhard Madea, Asphyxiation, Suffocation,and Neck Pressure Deaths, 2020
This constellation presupposes an enclosed volume of air available for respiration. A self-contained volume exists where individuals are imprisoned in sealed containers, virtually airtight pieces of furniture or boxes. This special form of normobaric-O2 deficiency is occasionally referred to as entrapment in English forensic pathology. In the same way, placing a plastic bag over the head also results in a virtually enclosed volume of air. The limited volume leads to the repeated inhalation of expired air, a process also known as rebreathing. As the CO2 content equals approximately 0.04 per cent by volume in the atmospheric air and approximately 4.04 per cent by volume in the expiration, the proportion in the inhaled air increases rapidly. At the same time, the O2 content in the enclosed air volume decreases constantly until it reaches the lethal concentration of approximately 10 per cent by volume. The heightened CO2 content in the inhaled air leads to an increase in the respiratory rate, accelerating the asphyxiation process. A similar pathomechanism occurs in diving in the event of a malfunction in closed-circuit breathing apparatus.
Animal Toxicity Studies
Published in Nicola Loprieno, Alternative Methodologies for the Safety Evaluation of Chemicals in the Cosmetic Industry, 2019
Acute toxicity studies frequently are designed to express the potency of the toxicant in terms of the median lethal dose (LD50), a value representing the estimated dose causing the deaths of 50% of the animals exposed under the defined conditions of the test. In the case of inhalation acute toxicity tests, the toxicant potency is presented as the median lethal concentration (LC50), the estimated concentration in the environment to which the animals are exposed that will result in 50% mortality of the animal population exposed under the defined conditions of the test.
Carbon quantum dots nanoparticles deteriorate the antioxidant cellular status and stimulate DNA damage in tissues of the house fly Musca domestica larvae
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Mona Ragheb, Afaf A. Shalaby, Heba M. El-Sharkawy
Feeding method was the larval bioassay that was used in this study. Larvicidal activity of CQDNPs was evaluated according to Wright (1971) [16]. Larvicidal assays were based on exposing the third instar larvae of M. domestica to larval medium contaminated with CQDNPs. Twenty-five third instar larvae were placed in a plastic cup containing 10 gm of larval medium (wheat bran, yeast, powdered milk and water), and 10 ml of different serial concentrations of CQDNPs were added for each preparation. The serial concentrations of CQDNPs were 0.9, 3, 7 and 9 mg/ml, which were previously tested as lethal and sub-lethal concentrations that may cause approximate death of 10, 25, 50 and 90 of the tested population. For each concentration, four replicates were involved, for a total of 100 larvae. The numbers of the survived larvae were counted after 24 hours. The test included a set of control group (by adding dechlorinated water only to the larval medium). The lethal concentration (LC50) was calculated. The average larval mortality data was subjected to Probit analysis for calculating LC50 [17], other statistics at 95% fiducial limits of upper and lower confidence limit and chi-square values were calculated by using the software developed by Reddy et al. (1992) [18]. Results with p < 0.05 were statistically significant.
Evaluation of genotoxicity induced by herbicide pendimethalin in fresh water fish Clarias batrachus (linn.) and possible role of oxidative stress in induced DNA damage
Published in Drug and Chemical Toxicology, 2022
Priyanka Gupta, Sushant Kumar Verma
Determination of median lethal concentration (LC50) can be considered as most useful criterion of toxicity. The 96 h- LC50 value of pendimethalin for C. batrachus was determined as 3.55 mg/L which is similar to those obtained by Ahmad et al. (2000) in Nile tilapia (3.55 mg/L). However it was found to be 0.19 mg/L in bluegill sunfish and 0.138 mg/L in rainbow trout (USEPA 1996). These observed differences in obtained values of LC50 for different species were may be due to age, size and health (Abdul Farah et al. 2004) or physico-chemical parameters of water (Eaton and Gilbert 2008). LC50 of different toxicants may also differ with different species because of differences in toxicokinetics as well as toxicodynamics between the species (Rubach et al. 2011). Toxicokinetics include ability of a species to regulate the uptake of toxicant, detoxify it and finally eliminate it whereas toxicodynamics include interaction of the toxicant with enzymes and ability to repair damage. Concentration and formulation of chemicals are also important factors which can be considered during determination of median lethal concentration of a toxicant (Young and Woodside 2001).
Comparisons of acute inflammatory responses of nose-only inhalation and intratracheal instillation of ammonia in rats
Published in Inhalation Toxicology, 2019
Linda Elfsmark, Lina Ågren, Christine Akfur, Elisabeth Wigenstam, Ulrika Bergström, Sofia Jonasson
A sub-lethal concentration was decided on the basis of a small-scale pilot study where different concentrations were tested from 0.25% to 2.5% NH3 via i.t. instillation and the lung injury was evaluated at 24 h post-exposure. A final concentration of 1% NH3 (25% weight percent NH3, Merck Eurolab AB, Sweden) diluted in water, with a pH 11.75 at room temperature (approximately ≥90% un-ionized NH3 in the solution (Emerson et al. 1975)), was chosen for the study. The rats were anesthetized briefly using enflurane before NH3 was administered by i.t. instillation in a volume of 200 μl. Control rats, given only the solvent, did not show any response different from unexposed healthy rats. In the full-scale rat study, the concentration of 1% NH3 was used and its effects were evaluated at 5 h, 24 h, 14 days, or 28 days post-exposure. Data regarding body weight, cells in BALF, inflammatory cytokines, organ weights, respiratory mechanics, collagen deposition, and histopathology are shown for all animals.