1 Introduction
Pharmaceuticals constitute a structurally diverse class of mostly synthetic organic
compounds that have been designed and optimized for their efficient and selective
interaction with a specific macromolecular target whose modulation has been demonstrated to result in the desired pharmacological response in the treated organism.
In case of drugs for the diagnosis, prevention, and treatment of medical conditions in
humans, the ultimate goal of all research and development efforts in industrial
settings is to deliver medicines with proven efficacy and safety for a given indication. Therefore, drugs receiving marketing authorization from the regulatory agencies have undergone extensive testing in clinical trials involving large number of
patients to fully satisfy the two aforementioned essential requirements. As desirable
as it may appear from an environmental perspective, pharmaceutical compounds are
designed in the first place to improve the health of human beings according to the
treatment plan with a given route of administration. In many cases this means that
high metabolic stability in the human body is a desirable feature; only when the rate
of biotransformation is low enough can systemic exposure at an acceptable dose be
achieved. If drug metabolism is extensively studied at the drug discovery stage,
including the elucidation of metabolic pathways and the identification of the
enzymes responsible for each of the reactions, then these investigations aim at
gaining a broad understanding of the clearance mechanisms as part of the overall
characterization of the elimination routes and at assessing the potential of drug-drug
interactions in clinical settings. Whether a drug is extensively metabolized or rather
excreted in unaltered form from the human body is indeed an important characteristic of the compound, but directing its design toward one pathway or the other is not
a goal per se. In other words, whatever the excretion profile looks like, drug safety in
the narrow sense essentially ends once all drug-related material has been eliminated
from the human body. At this very moment, though, it may become an environmental problem.
After more than two decades of extensive studies on the environmental occurrence, distribution and fate of drugs, and the generation of a huge body of literature
on these topics, it is an undeniable matter of fact that the large majority of sewageborne drugs are incompletely removed from the waste stream ultimately finding their
way into the aquatic environment, or, if the treated wastewater is reused in agriculture for irrigation purposes, they can become soil contaminants.
2 Presence of Drugs in Soils and Their Remediation
Soil is an environmental compartment, which is exposed to PhACs residues through
TWW reuse and acts as a sink facilitating their secondary transfer to others compartments (e.g., soil-living organisms and plants). More research is needed to
quantify the current risk of PhACs in wastewater reuse systems, in particular
526
S. Pérez et al.
Pharmaceuticals constitute a structurally diverse class of mostly synthetic organic
compounds that have been designed and optimized for their efficient and selective
interaction with a specific macromolecular target whose modulation has been demonstrated to result in the desired pharmacological response in the treated organism.
In case of drugs for the diagnosis, prevention, and treatment of medical conditions in
humans, the ultimate goal of all research and development efforts in industrial
settings is to deliver medicines with proven efficacy and safety for a given indication. Therefore, drugs receiving marketing authorization from the regulatory agencies have undergone extensive testing in clinical trials involving large number of
patients to fully satisfy the two aforementioned essential requirements. As desirable
as it may appear from an environmental perspective, pharmaceutical compounds are
designed in the first place to improve the health of human beings according to the
treatment plan with a given route of administration. In many cases this means that
high metabolic stability in the human body is a desirable feature; only when the rate
of biotransformation is low enough can systemic exposure at an acceptable dose be
achieved. If drug metabolism is extensively studied at the drug discovery stage,
including the elucidation of metabolic pathways and the identification of the
enzymes responsible for each of the reactions, then these investigations aim at
gaining a broad understanding of the clearance mechanisms as part of the overall
characterization of the elimination routes and at assessing the potential of drug-drug
interactions in clinical settings. Whether a drug is extensively metabolized or rather
excreted in unaltered form from the human body is indeed an important characteristic of the compound, but directing its design toward one pathway or the other is not
a goal per se. In other words, whatever the excretion profile looks like, drug safety in
the narrow sense essentially ends once all drug-related material has been eliminated
from the human body. At this very moment, though, it may become an environmental problem.
After more than two decades of extensive studies on the environmental occurrence, distribution and fate of drugs, and the generation of a huge body of literature
on these topics, it is an undeniable matter of fact that the large majority of sewageborne drugs are incompletely removed from the waste stream ultimately finding their
way into the aquatic environment, or, if the treated wastewater is reused in agriculture for irrigation purposes, they can become soil contaminants.
2 Presence of Drugs in Soils and Their Remediation
Soil is an environmental compartment, which is exposed to PhACs residues through
TWW reuse and acts as a sink facilitating their secondary transfer to others compartments (e.g., soil-living organisms and plants). More research is needed to
quantify the current risk of PhACs in wastewater reuse systems, in particular
526
S. Pérez et al.