**1. Introduction**

In the recent decades, the term "emerging pollutants" have been used widely to refer to a variety of chemical compounds without regulatory status in the environment and its impact on the environment and human health are poorly understood. Within the category of emerging pollutants, the antibiotics are one of the most significant groups.

Antibiotics are among the most successful drugs used for human therapy; however, these drugs are also recognized by its use and benefits in many different activities such as agriculture, aquaculture, bee keeping and livestock as growth promoters. Wise in 2002, estimated that the consumption in the market of antibiotics at worldwide level, was between 100,000 and 200,000 tonnes annually; however, the World Health Organization states that the amount of antibiotics is not precisely known because only a few countries have national statistics of the use, amounts and patterns of antibiotics [1–9].

Due to the extensive use in human and veterinary medicine, it is a reality that antibiotic compounds may be found in different environmental compartments. Indeed, in the last few years, antibiotics have been detected and reported by several researchers around the world in the µg/L range in municipal sewage, hospital effluents, sewage treatment plants effluents, surface water, ground water, marine water and drinking water [10–23]. The excretion of incompletely metabolized antibiotics by human and animals is the primary source of antibi‐ otics in the environment, and other sources include the disposal of unused antibiotics and waste from pharmaceutical manufacturing process; residential (private residences, dormito‐ ries, hotels and residential care facilities) and commercial facilities (including hospitals) are also known as contributors of antibiotics to municipal wastewater. Other potential contribu‐ tors of antibiotics to surface and groundwater are effluents from wastewater treatment plants and industrial facilities, and surface runoff from concentrated animal feeding operations [22, 24].

The occurrences of these compounds in different water bodies represent a potential threat to the environment, since these drugs are designed to have a pharmacological effect and to be persistent; moreover, the greatest concern about the presences of antibiotics in the environment is the emergence and dissemination of antibiotic resistance genes [1, 4, 12, 13, 16, 25–28].

In addition, antibiotics are of concern due to their high toxicity to algae and bacteria at low concentrations, potential genotoxic effects, disruption of aquatic ecology, promotion of antibiotic resistance and possibly even increased human health risks [20, 22, 29].

As a result, Sanderson et al. in 2004 classifies the antibiotics as pollutants of high priority for measuring environmental risk due to the probability of potential effects on human and environmental health, even more than sex hormones, cardiovascular drugs and antineoplastics [30].

Risk analysis is the scientific methodology used internationally to assess toxic effects on the environment [31–33]. In 2002, Jones et al. reported that the risk quotient (RQ) for amoxicillin in the United Kingdom exceeded the 1.00 unit, as well as, Park and Choi in 2008 reported that amoxicillin has a risk quotient (RQ) in Korea of 1.62, suggesting the need for further research to this antibiotic as an ongoing and future environmental monitoring toxicological investiga‐ tions [34, 35].

Likewise in 2004, Boxall et al. scored the amoxicillin as "high priority" in environmental monitoring and prioritization of toxicological studies [34–36].
