collembolans were clearly affected with an LC 50 of 8.4 mg/kg soil. Predatory mites
and earthworms were less sensitive to ivermectin with LC 50 s calculated to be greater
than or equal to 31.6 and 10 mg/kg soil, respectively. Meanwhile, climbazole, an
antifungal agent used in some antidandruff shampoos, was found to have no effect
on reproduction in springtails (Folsomia candida) at concentrations as high as
1,000 mg/kg soil dry mass [143]. However, climbazole did disrupt dehydrogenase
enzyme activity in the soil bacterium Arthrobacter globiformis with an EC 50 of
456 mg/kg soil dry mass.
8 Implications of Pharmaceutical Uptake in Terrestrial
Systems and Future Research Needs
Exposure to pharmaceuticals from both an ecosystem perspective (i.e. food chain
transfer) and an agricultural (i.e. human exposure) perspective has the potential to
result in a suite of unintended consequences. We are starting to drive more towards
increased water reuse and biosolid amendment practices. When coupled with the
observed effects of pharmaceuticals in terrestrial plants and invertebrates, at environmentally relevant concentrations, this suggests terrestrial systems are at risk from
pharmaceutical exposure. This is primarily a result of the bioactive nature of these
chemicals, where the chemical potency of pharmaceuticals is retained upon release
into the environment. However, as detailed above, contrasting findings exist
between the small number of phytotoxicity studies which have been currently
published. Differences between toxicological responses exist between test species
and experimental conditions for the same pharmaceutical. It is also important to note
that observed effects on a whole plant organ that consider a single end point
(e.g. germination) do not necessarily reflect effects on other important plant processes that ultimately regulate plant growth and development. More research,
characterising this risk using a wider variety of pharmaceuticals under environmentally relevant exposure scenarios, is urgently needed.
To date, pharmaceutical exposure in agricultural systems has been largely ignored
when it comes to developing wastewater reuse policy frameworks to support the
increasing adoption of sustainable agricultural practices, with a focus typically on
more traditional pollutants such as nutrients and metals. As highlighted by [144],
more research is needed to quantify the current risk of pharmaceuticals in wastewater
reuse systems, in particular where multiple receptors are considered, such as exposure to wildlife and the soil microbial community. This new knowledge will enable
the development of thresholds for safe reuse of wastewater treatment by-products.
The above discussion has drawn on research undertaken in countries that are
defined as high income (e.g. USA, Canada, Sweden, UK, Israel, Chile) or upper
middle income (e.g. China). However, the number of people living in low- and
middle-income countries (LMIC), excluding China, was 5 billion in 2018
[145]. There is a considerable difference in how wastewater is collected and treated
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
209
and earthworms were less sensitive to ivermectin with LC 50 s calculated to be greater
than or equal to 31.6 and 10 mg/kg soil, respectively. Meanwhile, climbazole, an
antifungal agent used in some antidandruff shampoos, was found to have no effect
on reproduction in springtails (Folsomia candida) at concentrations as high as
1,000 mg/kg soil dry mass [143]. However, climbazole did disrupt dehydrogenase
enzyme activity in the soil bacterium Arthrobacter globiformis with an EC 50 of
456 mg/kg soil dry mass.
8 Implications of Pharmaceutical Uptake in Terrestrial
Systems and Future Research Needs
Exposure to pharmaceuticals from both an ecosystem perspective (i.e. food chain
transfer) and an agricultural (i.e. human exposure) perspective has the potential to
result in a suite of unintended consequences. We are starting to drive more towards
increased water reuse and biosolid amendment practices. When coupled with the
observed effects of pharmaceuticals in terrestrial plants and invertebrates, at environmentally relevant concentrations, this suggests terrestrial systems are at risk from
pharmaceutical exposure. This is primarily a result of the bioactive nature of these
chemicals, where the chemical potency of pharmaceuticals is retained upon release
into the environment. However, as detailed above, contrasting findings exist
between the small number of phytotoxicity studies which have been currently
published. Differences between toxicological responses exist between test species
and experimental conditions for the same pharmaceutical. It is also important to note
that observed effects on a whole plant organ that consider a single end point
(e.g. germination) do not necessarily reflect effects on other important plant processes that ultimately regulate plant growth and development. More research,
characterising this risk using a wider variety of pharmaceuticals under environmentally relevant exposure scenarios, is urgently needed.
To date, pharmaceutical exposure in agricultural systems has been largely ignored
when it comes to developing wastewater reuse policy frameworks to support the
increasing adoption of sustainable agricultural practices, with a focus typically on
more traditional pollutants such as nutrients and metals. As highlighted by [144],
more research is needed to quantify the current risk of pharmaceuticals in wastewater
reuse systems, in particular where multiple receptors are considered, such as exposure to wildlife and the soil microbial community. This new knowledge will enable
the development of thresholds for safe reuse of wastewater treatment by-products.
The above discussion has drawn on research undertaken in countries that are
defined as high income (e.g. USA, Canada, Sweden, UK, Israel, Chile) or upper
middle income (e.g. China). However, the number of people living in low- and
middle-income countries (LMIC), excluding China, was 5 billion in 2018
[145]. There is a considerable difference in how wastewater is collected and treated
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
209