**1.1.1 Hazard identification**

This step can be defined as the qualitative determination of whether or not a particular hazardous agent is associated with health effects of sufficient importance to warrant further scientific investigations. Different kinds of tools (QSAR, short-term toxicity test) are used in order to estimate the chemical damage of a single substance. When establishing the hazard from industrial sources, the chemicals are also identified according to measurements of amount and typology of emissions.

### **1.1.2 Dose-response assessment**

This component is focused on examining quantitative relationships between the magnitude of the exposure (or dose) and the probability of occurrence of adverse effects in the population. Usually, dose-response assessment is based on extrapolations from data about laboratory animals, which have been given high-doses of toxicant and monitored accordingly.

### **1.1.3 Exposure assessment**

Exposure assessment may be defined as the quantitative determination of the extent of exposure of the population to the hazardous agent in question. Since they provide a real knowledge of the state of pollution of an area, data obtained in the environmental monitoring are commonly used as a starting point. Factors that need to be considered include frequency and duration of exposure, rates of uptake or contact, and rate of absorption (NRC, 1993). Other factors in assessing exposure include release patterns, cumulative versus non-cumulative exposure, persistence, failure of exposure controls, quality of data and quality of models.

#### **1.1.4 Risk characterization**

This fourth component can be defined as the description of the nature and magnitude of the risk, expressed in terms which are comprehensible to decision makers and the public. Information acquired in the previous 3 steps is integrated in order to communicate the overall meaning of, and confidence in, the hazard, exposure, and risk conclusions. Risk is expressed as a probability of suffering a particular kind of harm from a hazard to a specified group of population (Bennion *et al*., 2005). Moreover, qualitative and quantitative uncertainty related to risk must be also supplied.

Health Risk Assessment of Plasticizer in Wastewater Effluents and Receiving Freshwater Systems 195

Fig. 1. Map showing five of the five of the wastewater treatment plants.

Analytical grade phenol (PH) 99.9 %, 2-nitrophenol (2-NP) 99 %, 4-nitrophenol (4-NP) 99 %, 2,4-dinitrophenol (2,4-DNP) 99.7 %, 4,6-dinitro-2-methylphenol (DNMP) 98 %, 2,4 dimethylphenol (2,4-DMP) 98 %, 2-chlorophenol (2-CP) 99.8 %, 4-chlorophenol (4-CP) 99 %,

**2.2 Chemicals and reagents** 

The project aimed at determining the potential health risks that may be associated with using river water and treated effluent from wastewater treatment plants in Cape Town. Since phenols and phthalate esters were placed on the United State Environmental Protection Agency list as priority pollutants, both phenols and phthalate esters congeners were analyzed in water samples. However, emphasis is more on the phthalate esters congeners. The derivatization of the phenolic congeners did not in any way affect the intensity of the phthalate esters congeners included in this study (Olujimi et al., 2011b).
