Ibuprofen degradation was negligible in anaerobic and sterile soil [174] and watersaturated soil [119], further indicating that it is degraded by microorganisms and
principally under aerobic conditions.
Ibuprofen has been found in different terrestrial ecosystems [175, 176] at different concentrations ranging between 0.2 and 610 μg/kg. In soils ibuprofen is rapidly
degraded under aerobic conditions with half-lives values between 30 to 34.3 days,
10 to 15 days, and 1 to 6 days, respectively [38, 114, 119]. Similar maximum
mineralizable amounts of ibuprofen were shown in both aqueous and soil microcosms but with about 3.5 times lower mineralization rate in soil systems [120].
To our best knowledge, the effect of ibuprofen on microorganisms has only been
studied in liquid cultures and aquatic populations, and not yet on soil microorganisms. Ibuprofen has antifungal activity against dermatophytes [177] and inhibits the
growth of some Gram-positive species [178, 179]. Ibuprofen caused the decrease in
the biomass of riverine biofilms and inhibited the growth of Cyanobacteria and of
alpha, beta-proteobacteria, cytophaga-flavobacteria, and SRB385 populations
[180]. Additionally, ibuprofen was also shown to significantly modify the growth
of the microbial community of a river sediment incubated at different temperatures
and light exposure [181]. Pollution-induced community tolerance (PICT) analysis
performed on fluvial biofilms exposed to wastewater effluents showed that at the
highest concentrations of ibuprofen and diclofenac, they acquired a tolerance to
these components accompanied by an alteration of the algal composition and
metabolic profile of microbial organisms [182]. Recently, a mixture of ibuprofen,
naproxen, and diclofenac was shown to change the composition of the microbial
community (increase in Actinobacteria and Bacteroidetes and a decrease of
Micropruina and Nakamurella) but not the total nitrogen removal in batch reactors
[183]. Although the environmental risk assessment concluded that ibuprofen represents a risk for the aquatic environment [184], it was not included in the list of
priority substances under the Water Frame Directive due to a lack of sufficient
evidence for its environmental toxicity [185].
3.1.3 Diclofenac
Diclofenac, the most used NSAID in the world, is poorly removed in conventional
sewage treatment plants [186–188]. Hence, diclofenac residues are frequently
detected in the environment [53, 175, 189–192]. As a consequence, it is considered
as a contaminant of emerging concern, and it was added to environmental quality
standards (EQS) with a threshold value of 0.1 μg/L (European Community document (COM(2011)876)). More recently, diclofenac was included in the list of
priority substances (PSs) of the Directive 2013/39/EU and Watch List of Decision
2015/495/EU [193–195].
Diclofenac is a polar pharmaceutical compound poorly adsorbed to soil components and therefore easily transferable to surrounding environmental compartments
via leachates and runoff [38]. In agricultural soils, under aerobic conditions,
diclofenac is readily biodegradable [74, 114, 121–123] within 10 days, whereas it
Impact of PhACs on Soil Microorganisms
273
principally under aerobic conditions.
Ibuprofen has been found in different terrestrial ecosystems [175, 176] at different concentrations ranging between 0.2 and 610 μg/kg. In soils ibuprofen is rapidly
degraded under aerobic conditions with half-lives values between 30 to 34.3 days,
10 to 15 days, and 1 to 6 days, respectively [38, 114, 119]. Similar maximum
mineralizable amounts of ibuprofen were shown in both aqueous and soil microcosms but with about 3.5 times lower mineralization rate in soil systems [120].
To our best knowledge, the effect of ibuprofen on microorganisms has only been
studied in liquid cultures and aquatic populations, and not yet on soil microorganisms. Ibuprofen has antifungal activity against dermatophytes [177] and inhibits the
growth of some Gram-positive species [178, 179]. Ibuprofen caused the decrease in
the biomass of riverine biofilms and inhibited the growth of Cyanobacteria and of
alpha, beta-proteobacteria, cytophaga-flavobacteria, and SRB385 populations
[180]. Additionally, ibuprofen was also shown to significantly modify the growth
of the microbial community of a river sediment incubated at different temperatures
and light exposure [181]. Pollution-induced community tolerance (PICT) analysis
performed on fluvial biofilms exposed to wastewater effluents showed that at the
highest concentrations of ibuprofen and diclofenac, they acquired a tolerance to
these components accompanied by an alteration of the algal composition and
metabolic profile of microbial organisms [182]. Recently, a mixture of ibuprofen,
naproxen, and diclofenac was shown to change the composition of the microbial
community (increase in Actinobacteria and Bacteroidetes and a decrease of
Micropruina and Nakamurella) but not the total nitrogen removal in batch reactors
[183]. Although the environmental risk assessment concluded that ibuprofen represents a risk for the aquatic environment [184], it was not included in the list of
priority substances under the Water Frame Directive due to a lack of sufficient
evidence for its environmental toxicity [185].
3.1.3 Diclofenac
Diclofenac, the most used NSAID in the world, is poorly removed in conventional
sewage treatment plants [186–188]. Hence, diclofenac residues are frequently
detected in the environment [53, 175, 189–192]. As a consequence, it is considered
as a contaminant of emerging concern, and it was added to environmental quality
standards (EQS) with a threshold value of 0.1 μg/L (European Community document (COM(2011)876)). More recently, diclofenac was included in the list of
priority substances (PSs) of the Directive 2013/39/EU and Watch List of Decision
2015/495/EU [193–195].
Diclofenac is a polar pharmaceutical compound poorly adsorbed to soil components and therefore easily transferable to surrounding environmental compartments
via leachates and runoff [38]. In agricultural soils, under aerobic conditions,
diclofenac is readily biodegradable [74, 114, 121–123] within 10 days, whereas it
Impact of PhACs on Soil Microorganisms
273