‘Exploding’ use of 2,4-D in Africa

2,4-D

I was recently in southern Ethiopia conducting an evaluation of pesticide use in USAID-funded Farmer to Farmer programs managed by the Catholic Relief Services. As part of the evaluation, I was tasked with familiarizing myself with the list of pesticides approved for use in Ethiopia. One pesticide stood out; 2,4-D.

To many people, 2,4-D is just a herbicide that performs wonders against unwanted dicotyledonous plants that are an eyesore on otherwise plush lawns. The compound is known as 2,4-dichlorophenoxy acetic acid. Originally developed during World War II for the purpose of increasing crop yield by suppressing weeds, 2,4-D was later introduced commercially in 1946 and soon became the most widely used herbicide globally. In fact, 2,4-D was the first ‘selective’ herbicide that eliminated dicotyledonous plants such as dandelions and pigweeds without harming monocotyledonous crops, such as maize, wheat, rice, barley, and teff. When 2,4-D is applied on a susceptible plant, it causes the plant to grow uncontrollably which results in the destruction of vital plant tissues leading to death. The effect of 2,4-D on a plant is considered to be like a cancer.

Having the distinction of being the first commercially available herbicide, 2,4-D is still widely used in agriculture as well as home and garden sectors. In the US, 2,4-D-tolerant crops have been introduced due to the belief that glyphosate-tolerant crops are reaching the end of their life cycle due to the proliferation and abundance of glyphosate-resistant weeds. With increased use of 2,4-D expected, the likelihood of more 2,4-D-resistant weed species developing may lead to the possibility of this herbicide having a similar fate as glyphosate and become obsolete in future.

DSCF1211

Field of teff  in southern Ethiopia.

In southern Ethiopia, farmers have become highly dependent on 2,4-D to keep their cereal crops free of dicotyledonous weeds. The level of exposure to 2,4-D is presumably high but the impacts on human and environmental health are unknown since no follow-ups are made after the herbicide has been sold. Nonetheless, the following observations were made during my evaluation:

  • Disappearing honeybee populations – which may be attributed to 2,4-D applications that eliminate plants that would otherwise serve as nectar sources for honeybees.
  • The herbicide is no longer working – which may indicate there is some tolerance or resistance to 2,4-D or perhaps the applications were made erroneously due to a number of reasons that may include calibration, application timing, etc. Another reason could be the quality of the 2,4-D being applied.

Of most importance, however, was the fact that most Ethiopian farmers tended NOT to use personal protective equipment (PPE) when they applied 2,4-D because they felt that the herbicide was ‘safe’ and PPE was unnecessary. But is it?

We know that 2,4-D can:

  • irritate the eyes and skin upon exposure,
  • induce coughing, cause dizziness and temporary loss of muscle coordination when inhaled for a prolonged period, and
  • impede the normal action of estrogen, androgen, and thyroid hormones, and is classified as an endocrine disrupting hormone.

At this point you may be wondering if there are known chronic effects of 2,4-D. Researchers have observed apparent links between 2,4-D exposure and non-Hodgkin’s lymphoma (a blood cancer) and sarcoma (a soft-tissue cancer) (Ibrahim et al., 1991). The link is not very strong and requires further study. However, in 2015, the International Agency for Research on Cancer declared 2,4-D a possible human carcinogen based on evidence that it damages human cells and causes cancer in laboratory animals in a number of studies (http://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr236_E.pdf).

There is no question that the current usage of 2,4-D in Ethiopia and elsewhere in Africa raises concern. Whenever 2,4-D is sprayed there is a high likelihood that the herbicide spray will drift, partly because the chemical is volatile, and affect unintended targets. The first line of defense is to increase the pesticide knowledge in communities where 2,4-D is used widely. Then, at minimum, adequate access to and availability of PPE must be ensured.

Reference:
Ibrahim, M. A., G. G. Bond, T. A. Burke, P. Cole, F. N. Dost, P. E. Enterline, M. Gough, R. S. Greenberg, W. E. Halperin, E. McConnell, I. C. Munro, J. A. Swenberg, S. H. Zahm, and J. D. Graham. 1991. Weight of the evidence on the human carcinogenicity of 2,4-D. Environ Health Perspect 96: 213–222.
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SUPESTA (www.supesta.com) confronts the challenge of pesticide use in Africa. We:
  • work with smallholder farmers, agro-dealers, extension personnel and others who routinely apply pesticide and help them build a knowledge base in pesticide use and safety,
  • promote alternative approaches to total reliance on pesticides, such as integrated pest management, and
  • help develop easily accessible tools that provide information on pesticide handling.
  • Ultimately, less harm will come to humans and the environment when pesticides are used by knowledgeable people. 

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