Urinary PAH Metabolites as Potential Biomarkers for PAH Exposure - A Pilot Study in Three Cities of Southern India

Research Article

Austin Environ Sci. 2017; 2(2): 1023.

Urinary PAH Metabolites as Potential Biomarkers for PAH Exposure - A Pilot Study in Three Cities of Southern India

Solaraj G and Mohanraj R*

Department of Environmental Management, Bharathidasan University, India

*Corresponding author: R Mohanraj, Department of Environmental Management, Bharathidasan University, India

Received: July 05, 2017; Accepted: August 03, 2017; Published: August 10, 2017


Polycyclic Aromatic Hydrocarbons (PAHs) are the large group of organic compounds with benzene rings that are mainly emitted during incomplete combustion of organic materials such as fossil fuels. Many PAHs are linked to carcinogenicity and mutagenicity and their presence in ambient air is an increasing day by day particularly in developing countries. In urban regions, more number of people are exposed to the PAHs since the emission sources of PAHs are many including vehicular emissions. Understanding the health impacts of PAHs in human beings is one of the challenging tasks which include laborious experiments. As an easy approach, biomarkers of PAH exposure offers an immediate insight into exposed population by simple methods. In the present study, we analyzed urine samples of 30 volunteers in three different cities of Southern India for PAH metabolites that are considered as potential biomarkers for PAH exposure. The presence of 2-hydroxynaphthalene (2-NAP) and 1-hydroxypyrene (1-OHP) in majority of samples indicated that a substantial population might be exposed to PAHs.

Keywords: PAH; Biomarkers; Urinary Metabolites


Biomarkers have been increasingly recognized worldwide for exposure assessment of hazardous chemicals. Particularly in exposure assessment the exogenous substance or first metabolite or the product of an interaction between a xenobiotic agent and some target molecule or cell that is measured as an indicator of an inherent or acquired ability of an organism to respond to the challenge of exposure to a specific xenobiotic substance [1]. In many cases, biomarkers can also serve as indicators of preclinical conditions, and demand the need for a detailed assessment. Biomarker assessment is also considered as advantageous and quick technique over the laborious dose-effect studies. Recent attention in epidemiology focuses on understanding the genetic basis for individual susceptibility to the development of chronic disease and interaction with the biomarkers of exposure [2]. Genetic susceptibility markers are very useful for addressing gene– exposure (i.e., gene–environment) interactions.

In evaluating the health effects and risks of PAH, great advances have been achieved in the development of various types of biomarkers, including chemical-specific biomarkers of exposure and characterization of genetic variation in many genes of relevance to carcinogenesis [3]. The most commonly used biomarkers of PAH exposure includes hydroxylated PAH metabolites in urine (OHPAHs, 2-naphthol, 2-hydroxyfluorene, 3-hydroxyphenanthrene, 1-hydroxypyrene, 6-hydroxychrysene and 3-hydroxybenzo[a] pyrene) [4].

The assay for the glucuronide conjugate of 1-OHP (1- OHPG) has been developed and successfully applied to population with various PAH exposures. 1-OHPG is more sensitive than 1-OHP, since 1-OHPG is 3–5 times more fluorescent than 1-OHP. On the other hand, the 1-OHPG assay requires more urine than the 1-OHP assay. Urinary 2-naphthol, a stable PAH metabolite, reflects more specifically ambient PAH exposure, whereas 1-OHP levels can be affected by diet and smoking. Thus, urinary 2-naphthol is suggested as a specific marker for exposure to airborne particulates whereas urinary 1-OHP has been used as a marker for exposure to PAHs by non-specific exposure routes [2].

While evaluating the occupational exposure of PAHs, [5] observed that waste incineration workers showed higher level of 1-OHP and 2-naphthol than the automobile emission inspection workers in Korea. The levels of 1-OHP in automobile emission inspectors, waste incineration workers and control subjects were 0.298 ± 0.212, 0.531 ± 0.427 and 0.061 ± 0.094 μmol/mol creatinine, respectively. The mean values of 2-naphthol were 5.894 ± 4.683, 8.947 ± 5.931 while compared to control 1.924 ± 3.441 mol/mol creatinine, which ascertained that biomarker is a potential tool for exposure studies. In contrary to the belief that inhalation as a major route of exposure to PAHs, [6] in a study at Japan identified dietary exposure was significantly correlated with urinary 1-OHP excretion than inhalation. Biomarker experiments also revealed that the average concentrations of 1-OHP in the urine samples were higher smokers and passive smoker groups than that of the non-smoking group [7].

Zheng et al (2013) suggested hydroxylated PAH metabolites (OH-PAHs) as suitable biomarkers for wood smoke exposure. In an experiment involving nine volunteers, urinary OH-PAHs, except 1-hydroxypyrene (1-PYR), correlated with those of PM 2.5, levoglucosan and PAHs in personal PM 2.5 samples. In the children subjects also urine samples appeared to be the best biomarkers; a study in Ohio at 126 homes and 16 daycares observed associations between selected sociodemographic/lifestyle factors and urinary 1-OHPyr levels [8,9]. The median urinary 1-OHPyr level was 0.33 ng/ mL. Therefore, large number of studies on biomarkers have widely recognized PAH urinary metabolites as potential biomarkers for human exposure studies.

Materials and Methods

Urine samples (early morning) from 30 volunteers (10 each from 3 cities: Chennai, Coimbatore and Tiruchirappalli; Figure 1) were collected and analyzed for urinary PAH metabolites. During the sample collection, volunteers were requested information on health and living habits, such as age, height, weight, disease prevalence and smoking habits. Early morning urine samples were collected in bottles pre-cleaned with deionized water and 0.1 M Hydrochloric acid (HCl). The samples were taken immediately to the laboratory. Volunteer’s age were between 23 to 45 years, of which 80% are males and 20% females. All of them resided in urban environments