Pesticide residues found in some La Paz lettuce
What it found
Half of the lettuce samples from a La Paz market contained one or more pesticides, and one in five was above the maximum residue limit.
No pesticides were found in the potatoes or onions.
What they found
Studies in people
Daily intake estimates
Using survey answers from 55 consumers and 36 vendors, the authors estimated that people in La Paz eat about 3 g of lettuce a day on average, with large portions of 60 g for children and 120 g for adults.
Studies in people and animals
Exposure below safety levels
Even for the most contaminated lettuce, the estimated daily pesticide intake stayed below the acceptable daily intake and the acute reference dose for both adults and children. The combined measure for the two most contaminated samples reached up to 25% of the threshold for children.
Other findings
Residues in lettuce
Pesticides were found in 5 of the 10 unwashed lettuce samples and 4 of the 10 after washing. The pesticides detected were cypermethrin, chlorpyrifos, difenoconazole and lambda-cyhalothrin.
Above the limits
In 2 of the 10 lettuce samples, levels were above the maximum residue limit, both before and after washing. Those two samples each contained two or three pesticides at the same time.
Washing the lettuce
Washing lettuce for 5 minutes in a water bath lowered pesticide levels by about 45% on average, with reductions ranging from 13% to 70%.
Potato and onion
No pesticide residues were detected in any of the potato or onion samples.
What the authors conclude
“Despite the limitations mentioned, our investigation shows that half of the lettuce samples bought in La Paz, Bolivia, contained 1 or more pesticides, and one-fifth were above the MRLs.”
Also in their conclusions
- They say the results do not show an unacceptable health problem for Bolivian consumers eating lettuce, onions and potatoes bought in La Paz, but that 20% of lettuce samples above the maximum residue limit is still concerning.
- They advise that measures should be taken to improve food safety for consumers in La Paz, including accrediting Bolivian laboratories, doing more residue testing and setting up a national pesticide monitoring programme.
- They note that a person's total pesticide exposure comes from the whole diet, not just lettuce.
How it was done
Bolivia has no national programme for checking pesticide residues in food, and almost no data exist for foods other than tomatoes and breast milk. The authors wanted to see whether lettuce, onion and potato sold in La Paz carried residues.
They bought 10 lettuce, 10 onion and 10 potato samples from shops and market vendors in La Paz on one day in August 2015, and screened them for 283 pesticides. Half of each sample was washed and prepared as people normally eat it, and the other half was left unwashed.
What it can’t tell you
- All the samples were bought on a single day in the dry season, so the results may not reflect lettuce sold at other times of year.
- The study looked at pesticide levels in the vegetables, not at whether people who ate them became ill.
- The number of samples was small, and the authors say the exact size of any error in their measurements is hard to estimate.
Who paid
- Conflicts
- DECLARATION OF CONFLICTING INTERESTS: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosures and Ethics As a requirement of publication, authors have provided to the publisher signed confirmation of compliance with legal and ethical obligations including but not limited to the following: authorship and contributorship, conflicts of interest, privacy and confidentiality, and (where applicable) protection of human and animal research subjects. The authors have read and confirmed their agreement with the ICMJE authorship and conflict of interest criteria. The authors have also confirmed that this article is unique and not under consideration or published in any other publication, and that they have permission from rights holders to reproduce any copyrighted material. The external blind peer reviewers report no conflicts of interest.
- Authors work at
- University of Southern Denmark, Denmark; Technical University of Denmark, Denmark; Odense University Hospital, Denmark
The paper
- Title
- Pesticide Residues in Commercial Lettuce, Onion, and Potato Samples From Bolivia-A Threat to Public Health?
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Skovgaard M, Encinas SR, Jensen OC, Andersen JH, Condarco G, Jørs E (2017). Pesticide Residues in Commercial Lettuce, Onion, and Potato Samples From Bolivia-A Threat to Public Health?. Environmental health insights. doi:10.1177/1178630217704194Free full textPubMed 28469451DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error