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

Introduction
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.
Methodology
Selecting Sampling Points
The Enqelab Street connects Enqelab square to Imam Hossein Square. Considering that risk assessment is a
method based on residents' 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.
Results
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).
Conclusion
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.