Evaluation of Health Risk Assessment by Heavy Metals in the Ambient Air of Tehran

Annually, heavy metal pollution is increasing in the environment and this eventually causes serious hazards for health of human, animal and plant populations. Heavy metals with their harmful effects are the major pollutants in big cities. Tehran is a big city and faced with this problem. Heavy metals such as arsenic, iron, zinc, lead, cadmium, chromium, copper, manganese and nickel exist in the air of Tehran. These polluteants are inhaled by inhabitants and cause serious problems for human body. Among streets, roads and highways of the city, Enqelab Street is one of the busiest and particularly from Enqelab Square to Imam Hossein Square. In this study, the results of measuring heavy metals including arsenic, iron, zinc, lead, cadmium, chromium, copper, manganese and nickel in the air of the streetare presented with the health risk assessment from permanent and temporary residents in thearea. Moreover, the risk of developing cancer and non-cancer diseases caused by inhaling the polluted air with heavy metals was also estimated. Selecting Sampling Points The Enqelab Street connects Enqelab square to Imam Hossein Square. Considering that risk assessment is a method based on resident's health, the main crossroads and squares are selected as the sampling points. Therefore, sampling was performed in 5 stations: Enqelab square, Valiasr Crossroads, Ferdowsi Square, Piche Shemiran, and Imam Hossein Square. Sampling Method and Chemical Analysis In this phase, in order to determine the concentration of heavy metals (including arsenic, iron, lead, cadmium, chromium, copper, manganese and nickel), air samples were collected and analyzed in two different seasons (on February 7th 2013 and May 22nd 2013) during 8 hours from 5 stations. The entire process was performed according to OSHA-125G standard method. Quality Control of the Analysis In order to determine the quality of analysis methods, precision and accuracy were tested. The precision is from 3 to 17 percent and average percent recovery isv aried between 83 and 97 percent.This is placed within the acceptable range of US Environmental Protection Agency guidelines. Overview of Risk Assessment In this study, the average value of the air inhaled by one inhabitant in Tehran is measured so that by calculating the air pollutant concentrations, the amounts of heavy metals which are entered into his body are obtained. For this purpose, three groups of people are defined in terms of the type and the amount of exposure to pollutants (heavy metals): permanent residents (from Enqelab Square to Imam Hossein Square), shopkeepers, vendors and employees and also students. Calculating the Risk of Developing Cancer and Non-Cancer Diseases In this phase, after providing all the required information, the risk of developing cancer and non-cancer diseases is calculated using following equations. The results of analyzing heavy metals in Enqelab Street’s air are presented and discussed. In figure 1, variations of the mean concentrations of the mentioned metals are provided in the form of a chart. Risk Assessment Results In Enqelab Street, hazard index for chronic and acute exposure is below 1 which shows no adverse effects on non-cancer disease (figure 2, 3). In addition, the total number of the residents at high risk of developing cancer (types of cancer) by inhaling the heavy metals in their lifetime was estimated to be lower than 24 out of 1 million people. This statistic shows that the conditions have not yet been dangerous. Therefore, through multiplying the rate of carcinogenesis by the number of each group, the total number of heavy metal induced cancers is obtained. In this study, the total number of cancers is three, thus the overall risk is allocated to pollutants including arsenic, cadmium, nickel and lead (figure 4). According to the presented results, the level of heavy metals in the air of Enqelab Street is not hazardous to the health of the residents. Therefore, there is no need to spend enormous expenses in this area. Nevertheless, the health of permanent and temporary residents is threatened by chromium and arsenic due to their high rate of carcinogenesis. The outcome of these investigations indicates that despite recording few different values in some places, the air pollution levels are equal in whole the area, from Enqelab Square to Imam Hossein Square. However, the air pollution level of ValiasCr rossroads is relatively considerable. This difference only has resulted from high volume of traffic in the crossroads. Unfortunately, traffic of students in this area is so heavy that solving Valiasr Crossroads traffic issues are considered as an important priority.