When considering the presence of pesticides in our environment, you might think about the outside world: soil, groundwater, sediment and crops are all contaminated with pesticide residues. But pesticides are also present in the indoor environment and accumulate in house dust. Researchers from CIEMAT have analyzed 128 dust samples from farmer households and 40 samples from non-farmer households. Results were remarkable: Even samples from non-farmer households contain 57 different pesticides (median). Many of these compounds have been banned from agricultural application in Europe, but can persist in house dust for extensive periods of time.. Not a single sample was free from pesticide residues.

Almost half of the pesticides measured are recognized as highly hazardous, and their presence in indoor dust may be of risk to human health. Potential effects of exposure to these pesticides include reproductive effects and hormone disturbances, irritation of the skin, eyes and respiratory tract, and cancer. Exposure to pesticides can also impact the gut microbiome. People and pets may be exposed to low concentrations of pesticide residues via inhalation of house dust, but also through accidental ingestion. It is estimated that the ingestion of indoor dust is approximately 30 mg/day for adults and 60 mg/day for children. For some compounds, ingestion of dust might be the main route of exposure. 

The scope of contamination

The farmers participating in this study were from 11 different case study sites in SPRINT, located throughout Europe and in Argentina, and the non-farmer participants were neighbours of farmers and ‘consumers’ living further away from farmland in France and Denmark. The participants were asked to collect the dust from their house during a period of a month, via vacuum cleaning. The presence of 198 pesticides was evaluated; 197 compounds were detected in the samples, demonstrating a huge variety of compounds found in house dust. The number of different pesticide residues detected in each sample ranged between 25 and 121 for farmer households and between 36 and 80 for neighbour and consumer households.

Conventional farms using plant protection products exhibited significantly higher numbers of different pesticide residues (80 residues/sample, median) compared to organic farms (65 residues/sample, median) and non-farmer households (57 residues/sample, median), and total concentration was also significantly higher on conventional farms.

Types of pesticide residues detected

17% of the tested compounds were present in more than three quarters of all of the farmer-household samples. Multiple pesticides were even detected in >99% of samples: The insecticides fipronil and imidacloprid, the fungicides fludioxonil, hexachlorobenzene, azoxystrobin, carbendazim, tebuconazole, and a synergist, piperonyl butoxide.

The presence of some of the compounds cannot be explained by recent pesticide applications in the area. Interestingly, imidacloprid and hexachlorobenzene were not approved as a plant protection product at time of this study. However, imidacloprid is often used to treat pets against fleas. In this study, 69% of the farmer participants owned pets, which might explain the high presence of imidacloprid. Hexachlorobenzene has a long field half live, and its presence in dust could reflect historical application of the compound.

Potential human health effects

Glyphosate, pyrethroids and the synergist piperonyl butoxide were found in the highest concentrations. Exposure to these compounds is a risk for human health; Glyphosate and some pyrethroids are possible carcinogens and hormone disruptors and are known to impact the gut microbiome. Piperonyl butoxide is also a known endocrine disruptor and known neurotoxicant. While concentrations of individual pesticides in house dust are relatively low, total concentrations of up to 283 μg/g where measured, which is high compared to other matrices measured in SPRINT. Not much is known about potential health effects of combined exposure to low concentrations of a large number of compounds. Imagine you can handle drinking 4 beers, or 3 glasses of wine, or 1 glass of whiskey, but what would happen if you drank all of them at the same time, every single day? SPRINT researchers are especially interested in elucidating the effects of these ‘cocktails’ on human health, as combined exposure is not taken into account when approving plant protection products for agricultural application. Clarifying these effects can assist future policies for pesticide application. The ultimate goal, of course, is to ensure food availability while protecting human health.

Sources:

Navarro I, De la Torre A, Sanz P, Baldi I, Harkes P, Huerta-Lwanga E, Nørgaard T, Glavan M, Pasković I, Pasković MP, Abrantes N…, Martínez, MA. Occurrence of pesticide residues in indoor dust of farmworker households across Europe and Argentina. Science of the Total Environment. Dec 20;905:167797 (2023). https://doi.org/10.1016/j.scitotenv.2023.167797

Silva V, Gai L, Harkes P, Tan G, Ritsema CJ, Alcon F, Contreras J, Abrantes N, Campos I, Baldi I, Bureau M, Christ F, Mandrioli D, Sgargi D, Pasković I, Polić Pasković M, Glavan M, Hofman J, Huerta Lwanga E, Norgaard T…, Geissen V  Pesticide residues with hazard classifications relevant to non-target species including humans are omnipresent in the environment and farmer residences. Environment International. Nov 1;181:108280 (2023)  https://doi.org/10.1016/j.envint.2023.108280

Icon credits:
Vacuum, hormone, cancer ribbon: flaticon.com

Inhale icon: Pike Picture from Noun Project

Ingest icon: Andrew Doane from Noun Project

Gut icon: Imron Sadewo from Noun Project