exposure via artificially spiked or natural wastewater, in an attempt to understand the
impacts of wastewater reuse schemes increasingly used in agriculture [10, 11]. Other
field experiments have studied the uptake of pharmaceuticals following the land
application of organic fertilisers such as sewage sludge (biosolids) and manure
(e.g. [12, 13]). Antibiotics are typically the most abundant pharmaceuticals detected
in plants following soil amendments with manure, a result of their high usage in
agricultural husbandry, which are commonly used as agricultural fertilisers.
A variety of crop types including roots, shoots, stems and fruits have been shown
to accumulate a range of pharmaceuticals. Studies have reported highly variable
rates of accumulation with concentrations ranging from no detection to low μg/kg
concentrations in an environmentally relevant exposure scenario. As highlighted in
Tables 1 and 2, there has been a focus on edible crops that require minimal
processing, such as vegetables with fewer studies evaluating the uptake and accumulation in grain crops such as maize and wheat. In addition, studies have typically
worked to define whole organ accumulation, such as leaf tissues, rather than
demonstrating cellular accumulation [34, 35].
Short-term laboratory exposures are typically used to provide mechanistic insight
into the uptake of pharmaceuticals (e.g. [5]) as well an evaluation of the formation of
metabolites (e.g. [35, 36]) (see chapter “Impact of PhACs on Soil Microorganisms”).
Mechanistic studies also typically use hydroponics, where plants are grown in a
nutrient medium, thereby negating competitive sorption processes observed when
soil is present. Laboratory exposures allow for the evaluation of specific end points
following exposure in well-controlled conditions (e.g. growth chamber) where
temperature, light and humidity can be regulated. However, it has been argued that
this exposure lacks environmental relevance as it does not replicate natural environmental fluctuations. Generally, plant uptake studies are relatively short term
consisting of one crop cycle (i.e. fruiting or maturation) and have seldom considered
accumulation or toxicity resulting from a multigenerational exposure (i.e. from
contaminated seed).
To date, research has demonstrated that physiochemical properties of the pharmaceuticals, such as ionisable functional groups, have a profound impact on the
uptake, accumulation, translocation and transformation of pharmaceuticals in plants.
In addition, the plant species traits, soil properties which control the fate of the
chemical, water quality and experimental set-up (exposure duration, concentration
and pharmaceutical application) also affect the uptake and accumulation of these
chemicals.
The following discussion will give an overview of the uptake of pharmaceuticals
in plants and invertebrates through various exposure pathways, including from
spiked soils, wastewater irrigation and application of wastewater sludges, or biosolids. Factors that affect the uptake of pharmaceuticals, such as plant species or the
physicochemical properties of the pharmaceutical and the environment, are
discussed along with implications of uptake, including biological transformation
and toxicity of pharmaceuticals. Finally, the geographic location of these studies is
considered throughout this chapter to identify where our current understanding is
applicable and where knowledge gaps need to be addressed.
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
177
impacts of wastewater reuse schemes increasingly used in agriculture [10, 11]. Other
field experiments have studied the uptake of pharmaceuticals following the land
application of organic fertilisers such as sewage sludge (biosolids) and manure
(e.g. [12, 13]). Antibiotics are typically the most abundant pharmaceuticals detected
in plants following soil amendments with manure, a result of their high usage in
agricultural husbandry, which are commonly used as agricultural fertilisers.
A variety of crop types including roots, shoots, stems and fruits have been shown
to accumulate a range of pharmaceuticals. Studies have reported highly variable
rates of accumulation with concentrations ranging from no detection to low μg/kg
concentrations in an environmentally relevant exposure scenario. As highlighted in
Tables 1 and 2, there has been a focus on edible crops that require minimal
processing, such as vegetables with fewer studies evaluating the uptake and accumulation in grain crops such as maize and wheat. In addition, studies have typically
worked to define whole organ accumulation, such as leaf tissues, rather than
demonstrating cellular accumulation [34, 35].
Short-term laboratory exposures are typically used to provide mechanistic insight
into the uptake of pharmaceuticals (e.g. [5]) as well an evaluation of the formation of
metabolites (e.g. [35, 36]) (see chapter “Impact of PhACs on Soil Microorganisms”).
Mechanistic studies also typically use hydroponics, where plants are grown in a
nutrient medium, thereby negating competitive sorption processes observed when
soil is present. Laboratory exposures allow for the evaluation of specific end points
following exposure in well-controlled conditions (e.g. growth chamber) where
temperature, light and humidity can be regulated. However, it has been argued that
this exposure lacks environmental relevance as it does not replicate natural environmental fluctuations. Generally, plant uptake studies are relatively short term
consisting of one crop cycle (i.e. fruiting or maturation) and have seldom considered
accumulation or toxicity resulting from a multigenerational exposure (i.e. from
contaminated seed).
To date, research has demonstrated that physiochemical properties of the pharmaceuticals, such as ionisable functional groups, have a profound impact on the
uptake, accumulation, translocation and transformation of pharmaceuticals in plants.
In addition, the plant species traits, soil properties which control the fate of the
chemical, water quality and experimental set-up (exposure duration, concentration
and pharmaceutical application) also affect the uptake and accumulation of these
chemicals.
The following discussion will give an overview of the uptake of pharmaceuticals
in plants and invertebrates through various exposure pathways, including from
spiked soils, wastewater irrigation and application of wastewater sludges, or biosolids. Factors that affect the uptake of pharmaceuticals, such as plant species or the
physicochemical properties of the pharmaceutical and the environment, are
discussed along with implications of uptake, including biological transformation
and toxicity of pharmaceuticals. Finally, the geographic location of these studies is
considered throughout this chapter to identify where our current understanding is
applicable and where knowledge gaps need to be addressed.
Uptake and Effects of Pharmaceuticals in the Soil-Plant-Earthworm System
177