The grain industry must be concerned about possible endocrine-disruptive chemicals in pesticides and insecticides, says Prof Riana Bornman from the…
Speaking at the recent Agbiz Grain Symposium held in Pretoria, Bornman said the grain industry was listed as the entity that imported the highest number of insecticides and pesticides into South Africa.
An endocrine disruptor was a human-made chemical that interfered with any aspect of hormone action, she said.
The science for testing whether a chemical was an endocrine-disruptor was still in its infant stages.
Most information on it derived from epidemiological studies where workers or those living in specific areas were exposed to certain chemicals.
Especially pregnant mothers and infants were vulnerable to hormone-disruptive chemicals, Bornman said.
“Chemical producers are obliged to test whether a chemical is a carcinogen [cancer-causing], and if it could induce tumours or defects in a foetus. There are more than 140 000 chemicals in everyday use. Of these, only about 800 have been tested for endocrine-disruptive activity, and only for oestrogen, androgen and thyroid hormones,” Bornman said.
She said scientists’ traditional approach to toxicology has for years been a dose-dependent response.
This means a dose of a chemical was increased until at a certain level a response is found. But with endocrine disruptors, there may be negative effects long before one could observe them.
She said foetuses were especially vulnerable to hormones being disrupted at stages as early as one to six weeks, when the central nervous system developed, and at seven to 12 weeks, when the male reproductive system developed.
At this growth stage, a foetus needed testosterone to become male, otherwise it would continue as female.
If there was too little oestrogen or too little androgen at this stage, urogenital defects could develop, Bornman said.
She said decreasing male reproductive health and cancer linked to endocrine disruption was on the increase.
A chemical such as DDT was still widely applied in parts of South Africa to curb the spread of malaria, and it could hamper oestrogenic and foetus development. Bornman said many chemicals used in the grain industry had not been tested for possible endocrine-disruptive actions.
“Do not assume a chemical is safe until proved otherwise. Even in cases where no cause-and-effect relationship has been established by scientists, precaution is needed,” Bornman said.
She said if farmers used the guidelines given by associations such as the Fertiliser Association of South Africa, a huge difference would already be made to incidences of people being affected by endocrine-disruptive chemicals.
“Read the label and don’t use containers for other purposes, such as storing drinking water,” Bornman said.
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