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Januarie 2017
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ON FARM LEVEL
Natural resources and energy
These results were interpreted against guideline values (in the case
of inorganic constituents) or subjected to detailed risk assessment
methodologies (in the case of pesticides) so as to assess the poten-
tial risk of agricultural chemicals to human and animal health.
In addition, pesticides were prioritised based on quantity of use (QI),
toxicity potential to human health (TP) and hazard potential (HP),
which combine toxicity with environmental mobility. The data was
fed into an Excel-based risk indicator. When all three are combined,
the weighted hazard potential, which expresses the HP as a function
of the quantity of use of the pesticide, is determined.
‘It is a simple process enabling users such as water resource manag-
ers, catchment management agencies, water treatment works and
producers to prioritise pesticides at a national or crop-specific scale
according to any one of these indices.’
A further outcome of the study is a set of maps that give a spatial
overview of the likely distribution of specific active ingredients,
based on their application to crops and the distribution of those
crops throughout the country. It’s a first for South Africa. The maps
thus prioritise those areas that are likely to be of greatest con-
cern and can therefore make useful contributions to the design of
water quality monitoring programmes, interpretation of monitoring
data and as input into regional human health and ecosystem risk
assessments.
The impact of pesticides on human health
Concerning pesticides’ risk to human health, researchers actually
found levels to be ‘pretty low, with negligible risk associated with
consumption or use of water from the study areas’. Yet, there are
some warning signals. Despite the monitoring limitations mentioned,
the study revealed relatively high concentrations of particularly atra-
zine, terbuthylazine and simazine (all known endocrine disruptors) in
maize and sugarcane areas.
Samples collected in the Vals and Renoster rivers in particular
showed comparatively higher values than other study areas. Fur-
thermore, atrazine in particular was detected at similar concen-
trations over different seasons (wet and dry) indicating that it has
essentially saturated water resources in these catchments.
Though there was not much risk found from a human health per-
spective, it does require more research, particularly regarding
their potential endocrine disruptor effects, notes Dr Dabrowski. Bio-
assays conducted on water and sediment samples collected in the
study areas indicated ED activity on many occasions.
Dr Dabrowski cautions that it must be kept in mind that the re-
searchers did not look at all the listed pesticides and, where bioas-
says indicated endocrine disruptor effects, it was not possible to link
these to the use of a specific pesticide.
Pinpointing pesticide contamination
Maize is the most highly produced crop in South Africa and is
associated with high atrazine application.
A rural residential area with fruit orchards in close proximity.