Page 188 - Soil and water contamination, 2nd edition

Organic pollutants 175

male tadpoles and turns them into hermaphrodites with ovaries in their testes, much smaller
vocal organs and testosterone levels one-tenth of normal. Microbial degradation accounts for
most of the breakdown of atrazine, although the degradation rate is slow. As a result, atrazine
can persist in the environment for a long time, especially under dry or cold conditions.
Atrazine is not easily absorbed by soil particles. Despite being moderately soluble in water, it
is one of the most significant water pollutants in rain, surface, and groundwater, especially in
areas where it is intensively applied.
Alachlor, also called metachlor, is another herbicide, used to control annual grasses and
many broadleaved weeds on cropland. It is classified by the United States Environmental
Protection Agency as slightly toxic. It may cause slight skin and eye irritation in people
exposed to levels above the maximum contaminant level (MCL) in drinking water. Lifetime
exposure to levels above the maximum contaminant levels may result in liver and kidney
damage. Its carcinogenic effects remain uncertain. In soil, the breakdown of alachlor
occurs primarily through biodegradation. Its half-life in soil ranges from about 8 to15
days. Alachlor is highly to moderately mobile in soil and its mobility in soil decreases with
increasing soil organic carbon and clay content. Consequently, alachlor is widely detected in
surface water and groundwater in the vicinity of farms where it has been applied. In water,
alachlor is lost through photodegradation and biodegradation, although photodegradation
takes place only in shallow, clear surface water. Alachlor does not bioaccumulate in aquatic
organisms.

9.7.2 Pharmaceuticals and Personal Care Products

Pharmaceuticals and Personal Care Products (PPCPs) are a diverse category of ESOCs
comprising prescription and non-prescription drugs, diagnostic agents used in medicine,
caffeine and nicotine, and the ingredients of dietary supplements, soaps, conditioners,
cosmetics, fragrances, and sunscreens. PPCPs also include veterinary antibiotics. The
most important pathways of PPCPs to the environment are wastewater discharges, the
application of sewage sludge and manure as a soil conditioner and fertiliser, and landfill
leachate. Given the variety of compounds present in PPCPs, it is not possible to generalise
their environmental fate and impacts. The substances in PPCPs that attract most concern,
however, are the compounds that are water-soluble, are not readily sorbed to soil and
sediment particles, and are only slowly biodegradable.
PPCPs that are excreted or disposed by humans and washed away in wastewater, such
as caffeine, pain relievers (e.g. ibuprofen), antidepressants, birth control pills, drugs used
in chemotherapeutic cancer treatment and stimulant drugs (e.g. cocaine) can typically be
traced downstream of urban areas. The effectiveness of wastewater treatment in removing
these compounds from the effluent water depends on the type of wastewater treatment and
the physico-chemical properties of the specific ingredients of the PPCPs. Concentrations of
-1
PPCPs in the receiving water typically range from nanograms per litre (ng l ) to micrograms
-1
per litre (μg l ), with the highest concentrations typically being those of common pain
relievers and caffeine.
Veterinary antibiotics, hormones and other animal-growth regulators which are
incompletely metabolised and excreted in livestock urine and manure can be traced in
soils and groundwater beneath intensive agricultural areas. This may pose a threat to
human health if the groundwater is abstracted for drinking water. Although in most
cases groundwater contamination by veterinary drugs is not an acute health concern, the
long-term health and environmental effects are largely unknown. One of the potential
environmental hazards is the development of antibiotic-resistant microorganisms due to the
presence of antibiotic contaminants.

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