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Pinpointing pesticide contamination
and the damage it can do to people
I
n a South African first, a Water Research Commission (WRC)
study has created agricultural pesticide maps for improved risk
management.
As with many developing countries, agriculture remains vitally im-
portant to South Africa’s economy. Though it has decreased as
a percentage of gross domestic product (GDP) over the past four
decades, currently contributing around 2%, the sector formally
employs 638 000 people, and an estimated 8,5 million people are
directly or indirectly dependent on it for an income. The sector’s sig-
nificance is a key focus of the New Growth Path, a governmental
strategy to create five million new jobs by 2020.
Yet, the sector is impacting negatively on the resource that it is
most dependent on – our limited freshwater supplies. Regardless of
limited monitoring studies, there is sufficient information to indicate
that agricultural pesticides enter surface and groundwater.
According to the latest Department of Agriculture, Forestry and
Fisheries (DAFF) database, there are in excess of 8 000 herbicide,
insecticide and fungicide products registered for use in South
Africa. Many of these include active ingredients that are either car-
cinogenic or classified as endocrine disruptors (EDs), while for most
pesticides these endpoints have yet to be defined.
This is particularly concerning considering that many communities
do not have any or reliable access to treated water, and often make
use of water collected directly from the resource for drinking pur-
poses. Given the potential human health effects associated with ex-
posure to agrochemicals and their intensity of use, in combination
with the questionable supply and quality of drinking water in many
South African communities, it is important to identify and prioritise
pesticides that are particularly toxic and areas where people may
be exposed to these priority chemicals.
‘We know that these things do enter the water and much research
focus has been on the impact on the aquatic ecosystem,’ notes
Dr James Dabrowski, principal researcher in Environmental Chemis-
try and Water Quality at CSIR.
‘We also need to focus on the potential effects on human health
with water as the pathway, and in particular the impact of current
pesticides,’ he says, pointing out that rather much work has been
done on pesticides banned for agricultural use, such as dichlorodi-
phenyltrichloroethane, popularly known as DDT.
Dr Dabrowski is the principal researcher of a WRC initiated project
to answer some of these questions. The five-year study, which was
concluded in 2015, aimed to determine the extent and the level of
contamination by agricultural chemicals in selected water resources
and also to determine their risk to animal and human health, both
in terms of toxicity and endocrine disruptor effects.
The study was led by the CSIR together with collaborators from
the universities of Pretoria and North-West, and made significant
advances in addressing knowledge gaps in managing the risks of
agricultural pesticides in South Africa.
According to Dr Dabrowski, the study involved multiple aspects,
including identifying the most problematic pesticides among
the huge amount registered, looking at their potential impact on
human health, identifying which ones are most likely to enter the
resources and identifying where in the country these pesticides are
being used.
Prioritising pesticides ac-
cording to risk and locality
The project selected three agriculturally
intensive catchments representative of
important commercial crops produced in
South Africa, namely maize, sugarcane, cit-
rus and subtropical fruit.
The study areas were the Letsitele catch-
ment in the vicinity of Tzaneen, an area
dominated by tropical and citrus fruit pro-
duction, the Lomati catchment which drains
into the Komati River in the vicinity of Ko-
matipoort (dominated by sugarcane pro-
duction as well as by other tropical and
citrus fruits) and the Vals and Renoster
catchments in the Free State, both of which
enter the Vaal River in the vicinity of Kroon-
stad and Viljoenskroon. The latter is an
area of intensive maize production.
Seasonal sampling for endocrine disrup-
tor bioassays and organic and inorganic
constituents from surface water resources,
sediments and groundwater in the three se-
lected sites were conducted.
21
January 2017
ON FARM LEVEL
Natural resources and energy
Risk management / Freshwater supplies
PETRO KOTZÉ,
Water Research Commission (WRC)
Figure 1: One of the maps that provides a spatial overview of the likely distribution of specific active
ingredients (in this case atrazine), based on their application to crops and the distribution of those
crops throughout the country.