Use of LC50 in aquatic regulatory toxicology-Disharmony in global harmonization of hazard classification of chemicals

In regulatory aquatic toxicology, acute toxicity studies with chemicals are conducted with a species of fish, crustacea, and or alga. The LC50/EC50 obtained from these studies is used for the hazard classification and labeling of the chemicals. The methods like probit or logit analysis and Litchfield and Wilcoxon method are prescribed in the OECD guidelines to determine the LC50. In the present study, LC50s were calculated using probit analysis, Litchfield & Wilcoxon method, and also using the method by Trevan (the inventor of median lethal dose) using three sets of concentration-mortality data of fish acute toxicity tests. The slopes of the concentration-mortality curves, fiducial limits (95% confidence interval) of LC50s, and ‘mode’ of the concentration-mortality curves were compared. Though the methods used in the study resulted in more or less similar LC50s, the LC10 and LC90, slopes and ‘mode’ differed considerably, indicating that LC50 does not reveal the exact toxicity profile of a chemical. The LC50 calculated using Finney’s probit analysis provides better information on the toxicity profile of a chemical than the LC50calculated by Litchfield & Wilcoxon method. While interpreting LC50, the mortality occurred below 16 % (eg.,LC10) and above 84 % (eg.,LC90), slope and ‘mode’ of the concentration-mortality curve may also be considered. It is worth having a relook at the current practice of hazard classification and labeling of the chemicals based only on LC50 in regulatory aquatic toxicology.

Study on Effect of Spheroidization on Hazardous Classification of ADN

In order to determine the influence of spheroidization process of Ammonium dinitramide’s hazard grade, the hazardous division of Ammonium dinitramide before and after spheroidization is studied by using hazard classification procedure for combustible and explosive substances and articles standard (WJ20405) and hazard classification method and criterion for combusitible and explosive substances and articles standard (WJ20404). The research results show that spheroidization process can significantly improve the temperature stability of Ammonium dinitramide and significantly reduce friction sensitivity and impact sensitivity of Ammonium dinitramide. So spheroidization process can reduce the hazardous of Ammonium dinitramide and improve the safe character of Ammonium dinitramide.

Классификация строительных материалов по пожарной опасности

Рассмотрены системы классификации, используемые в отечественной и европейской практике оценки пожарной опасности строительных материалов, при этом применяются как идентичные, так и отличающиеся методы испытаний. Представлен критический анализ подходов к классификации строительных материалов по пожарной опасности и показана возможность использования результатов стандартных испытаний для прогнозирования их поведения при реальном пожаре. Отмечено, что действующая в России система противопожарного нормирования строительных материалов положительно зарекомендовала себя с точки зрения влияния на безопасность людей.The main differences of the fire hazard classification systems for building materials accepted in Russia and the EU countries are considered. It is shown that these classification systems are based on test results following both almost identical and significantly different methods. The analysis of the possibility of predicting the behaviour of building material in a real fire is carried out based on the results of standard fire hazard tests. It is concluded that the data obtained from the results of standard tests cannot be fully used to describe the thermal-oxidative decomposition and burning of building material in a real fire. The analysis of criticism of the domestic classification system described in the scientific literature for classifying building materials as different fire hazard classes is presented. The specified criticism is based on the assertion that the methods used in the framework of the Russian fire hazard classification system for building materials do not regulate the definition of so-called “dynamic” indicators during testing that characterizes a change in a given measured value during testing. It is shown that, firstly, the use of dynamic indicators does not lead to a more complete and adequate assessment of the fire hazard of building materials, and, secondly, the methods used in the framework of the European classification system for building materials by fire hazard have significant uncertainty, including parts of the definition of the above mentioned “dynamic” indicators. Criticism of the Russian fire hazard classification system of building materials is examined regarding the fact that within the framework of one fire hazard class, indicators are collected that by their physical nature are in no way correlated and interrelated. To this, an answer is given that, firstly, the concept of “fire hazard of building material” implies a comprehensive assessment of all indicators that can affect the behaviour of the material in case of fire, with a subsequent contribution to the formation of its dangerous factors and, secondly, such an approach to classification meets international best practices, and in particular European ones. It is noted that the long-standing practice of fire-rated building materials in Russia, based on the current classification, has shown its adequacy and correctness.