Newborns with high exposure to pesticides during gestation have lower birth weights and a higher probability of low birth weight and preterm birth
An increasingly volatile climate coupled with growing demand for food means that developing technologies and policies that promote greater productivity in agriculture is essential. In fact, global food needs are expected to increase by 35% to 56% between 2010 and 2050 (van Dijk et al. 2022).
Agricultural intensification programmes seek to increase productivity through the efficient use of agrochemicals and crops that adapt to climate change. Farms use pesticides to combat fungi, pests, and crop diseases, some of them caused by climate change and globalisation. However, the available empirical evidence in medicine, environmental sciences and economics shows that agrochemicals can generate important adverse effects on the health of the population that works and lives near farms and on biodiversity (Gemmill et al. 2013, Camacho and Mejia 2017, Larsen et al. 2017, Jones 2020, Taylor 2021, Frank 2022, Dias et al. 2023). It is estimated that pesticides cause 200,000 deaths from acute poisoning each year, most of them in developing countries, as they increase the risk of contracting diseases such as cancer and damage neurological development, thus delaying the learning process and reducing cognitive ability (Svensson et al. 2013, UNHR 2017).
In recent decades, national governments and international institutions have adopted different initiatives to limit the use of pesticides and protect their populations. However, there are very few studies using information on large-scale communities showing a causal effect of pesticides on population health that can be used to guide public policies. In recent research (Calzada, Gisbert and Moscoso 2023) we shed light on the health effects of pesticides by examining the impact of aerial fumigation of banana plantations in Ecuador.
Banana plantations in Ecuador
Ecuador provides an excellent context for analysing the effects of pesticide use in agriculture. Ecuador is the world’s fifth largest banana producer, and the largest exporter. In the last few decades, national banana producers have dedicated significant efforts to increasing their efficiency and have adopted pesticides on a massive scale at different stages of the production cycle. In the early 1970s, producers started to use aerial fumigations to treat the disease known as Sigatoka Negra, the main fungal disease affecting banana fruit plants. Despite the effectiveness of fumigations in stopping the spread of this fungus, their environmental and health implications have raised major concerns (Defensoría del Pueblo 2019). Children and adult populations who live, attend school, or work near banana fields are exposed to high levels of pesticides via inhalation, ingestion, and by penetration through the skin, and this makes them vulnerable to different types of diseases. Public interest in this problem has prompted the regulation of aerial fumigations. Specifically, in 2012, the government of Ecuador approved a regulation that sets a protection distance between fumigated areas and neighboring households. However, the lack of enforcement capacity of the responsible authorities and the challenging climate conditions are likely to reduce the effectiveness of this measure (UNHR 2017).
Study design
Our study examines the effects of pesticides used in banana plantations in Ecuador on newborns’ health outcomes (weight at birth, gestational length, low birth weight, and preterm birth). Specifically, we use a difference-in-differences (DID) approach that exploits the seasonal changes in the fumigation of banana plantations as an identification strategy.
We use a dataset obtained from the National Register of Live Births for the period 2015–17, which contains information of the mothers’ residential addresses during pregnancy. Our analysis focuses on almost 51,000 mothers that during pregnancy resided within 2.5 kilometers of the banana plantations. In addition, we have information on the perimeter of each plantation and the amount of pesticides applied in each of them. We combine the information on the mothers’ locations, the perimeters of the plantations and the gallons of pesticides applied in the plantations to compute measures that reflect the newborns’ geographical and seasonal exposure to pesticides during gestation.
Figure 1 presents the geographical distribution of banana plantations in Ecuador. In the lower right image, the yellow areas are banana plantations that apply aerial fumigation, and the red dots are the mothers’ residences during pregnancy. Notice that examining the effects of pesticides while relying only on distance from the plantations would be problematic, as mothers’ residences are usually surrounded by several plantations at different distances and with different sizes. To address this situation, we compute the variable “Exposure Buffer” that accounts for the area in square metres of air-fumigated banana plantations close to the mothers’ residences, at different distances.
Our analysis shows that the newborns potentially most affected by pesticides were those born to mothers living within 150 metres of the nearest plantation and surrounded by a relatively large number of square metres of fumigated plantation. An important challenge for our analysis is the possibility that households located near the plantations had different characteristics than those living further away, which would make it difficult to separate the causal impact of pesticides from unobservable factors that may affect the health of newborns. We address this potential endogeneity issue by implementing a difference-in-differences (DID) analysis that exploits seasonal changes in fumigation intensity. Banana plantations are fumigated throughout the year, but the most intense fumigations occur during the rainy season, which is when the Sigatoka Negra fungus spreads most easily. We use monthly information on the gallons of pesticides applied to each plantation to identify the months with the most intense fumigations.
Figure 1: Mother’s locations and banana plantations in Ecuador (2015-2017)
Note: The upper right image presents the geographic distribution of newborns exposed to banana plantations. The lower images show in yellow the location of banana plantations and in red dots the mothers’ residences.
Figure 2 shows the birth weight gradient of the newborns’ Exposure Buffers (weighted square metres of banana plantations surrounding mothers’ residences). The figure presents separately the results for newborns gestated and not gestated in periods of intensive fumigations. We observe that newborns with high values of the variable Exposure Buffers and gestated in a period of intensive fumigations have lower birth weights than those gestated in a period of non-intensive fumigations. Taking this into account, the DID estimation compares the difference between newborns born to mothers living in geographically exposed areas who were gestated during intensive and non-intensive fumigation seasons, relative to the difference between newborns born to mothers living in geographically non-exposed areas who were gestated during the same two seasons.
Figure 2: Birth weight gradient of square metres of fumigated plantations
Note: Local polynomial regressions of birthweight on the number of square metres of fumigated plantations surrounding mothers’ residences. The vertical red line shows the 150 metres distance from the nearest plantations.
Intense fumigations harm newborns’ health
We find that newborns living close to the banana plantations and exposed to intensive fumigations during their gestational period have an average birth-weight deficit of between 80 and 150 grams relative to non-exposed newborns. Pesticides have a greater impact when intensive fumigations coincide with the first two trimesters of gestation. We also obtain stronger effects for male newborns, and for newborns born to mothers with none or basic schooling levels. Moreover, the exposure to pesticides reduces the number of gestation weeks and increases the odds of being born with low birth weight and of preterm delivery. In addition, we find that the exposure to pesticides reduces the number of gestation weeks and increases the odds of being born with low birth weight and of preterm delivery. We complement our analysis considering a subsample of mothers who had more than one child during the period examined to estimate a model with maternal fixed effects. This analysis exploits the difference in birth weight between siblings exposed and not exposed to intensive fumigations during gestation. We find that newborns exposed to pesticides have an average birth weight 327 grams lower than their non-exposed siblings.
Policy implications
Understanding the way in which pesticides affect the health of the population is essential to design the regulations of fumigation practices in different types of plantations across the world. Our findings highlight the urgency of enforcing the protection distances established in national legislations to guarantee the protection of neighbouring populations and plantation workers. It is also important to enhance pregnancy protocols in affected regions and to reinforce the information campaigns about the risks of exposure to pesticides for all the population.
References
Calzada, J, M Gisbert and B Moscoso (2023), “The Hidden Cost of Bananas: The Effects of Pesticides on Newborns’ Health”, Journal of the Association of Environmental and Resource Economists, 10(6): 1623-1663.
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