onte Carlo mô phỏng đánh giá rủi ro là một ý tưởng tương đối mới, có thể bằng cách tăng sức mạnh máy tính đã trở thành có sẵn cho các nhà khoa học môi trường trong những năm gần đây. Ý tưởng cơ bản là để có một tình huống mà có là một nguy cơ liên quan với một biến nhất định, chẳng hạn như tăng tỷ lệ mắc ung thư khi có những cấp độ cao của một hóa chất trong môi trường. Mức độ của hóa chất sau đó được mô hình hóa như một chức. | CHAPTER 11 Monte Carlo Risk Assessment Introduction Monte Carlo simulation for risk assessment is a relatively new idea made possible by the increased computer power that has become available to environmental scientists in recent years. The essential idea is to take a situation where there is a risk associated with a certain variable such as an increased incidence of cancer when there are high levels of a chemical in the environment. The level of the chemical is then modelled as a function of other variables some of which are random variables and the distribution of the variable of interest is generated through a computer simulation. It is then possible for example to determine the probability of the variable of interest exceeding an unacceptable level. The description Monte Carlo comes from the analogy between a computer simulation and repeated gambling in a casino. The basic approach for Monte Carlo methods involves five steps A model is set up to describe the situation of interest. Probability distributions are assumed for input variables such as chemical concentrations in the environment ingestion rates exposure frequency etc. Output variables of interest are defined such as the amounts of exposure from different sources the total exposure etc. . Random values from the input distributions are generated for the input variables and the resulting output distributions are derived. The output distributions are summarised by statistics such as the mean the value exceeded 5 of the time etc. There are three main reasons for using Monte Carlo methods 1 The alternative is often to assume the worse possible case for each of the input variables contributing to an output variable of 2001 by Chapman Hall CRC interest. This can then lead to absurd results such as the Record of Decision for a US Superfund site at Oroville California which specifies a clean-up goal of x 10-7 pg litre for dioxin in groundwater which is about 100 times lower than the drinking water .
