Likely sources of pesticide residues in the indoor house dust of farming households.

This article provides key messages about the presence of indoor dust in farming households, and what you can do to minimise pesticide exposure.  

Indoor dust was collected and analysed for pesticide residues in 128 homes of farmers and their families across ten European countries and Argentina. Residues of 198 pesticides and their degradation products were observed. For most contaminants, average detected residue levels were between 0.5 to 20 parts per million (µg/g). Glyphosate and pyrethroid-based insecticides were the most frequently found. In some countries, these residues were found in the homes of all farmer participants. We found that the frequency and levels were lower in homes at organic farms compared to conventional farm homes. However, we have not studied how it is possible that residues are found in homes to such extent, warranting further research.  

What is dust? 

Dust is a mixture of fine particles from soil and clay, air pollutants, textile fibres, animal hair, and more. 

How do pesticides get into our homes? 

Previous studies have suggested that residents take home pesticides as dirt under their shoes. For example, a study in the Netherlands analysed doormats and detected a wide range of pesticide residues. For seven of the detected pesticides, a moderate to high correlation was found between levels observed in doormats and residues detected in indoor floor dust collected by vacuum cleaners. In farm homes, these substances were related to fungicide applications on the farm.  

Some studies also suggest that pets may carry pesticides into the home – cat and dog ownership is a predictor for increased exposure to insecticides used as flea repellent such as fipronil. Products sold as veterinary drugs and biocides for pets may also become a source of indoor dust contamination. 

Another study in France found that indoor house dust can become contaminated with insecticides used for the preservation of wood.  

An additional source of contamination of pesticides indoors is the use of pesticides on plants and flowers for home decoration. These ornamental plants and cut flowers may have been treated with pesticides. There is currently no EU regulation to control residues in these products, unlike for most food items.  

Finally, and more obviously, is that some of us apply pesticides in our homes, sometimes maybe even without being fully aware – for example, when trying to control so-called ‘pest’ insects such as mosquitoes, fleas, and wasps.  

Why do we find so many pesticides in dust? 

Pesticides can cling to dust particles, which may include both long-banned, persistent chemicals still lingering in the environment and newer, less persistent pesticides. In the dry, dark conditions common in homes, even pesticides considered less persistent can remain stable for long periods. Since it's nearly impossible to eliminate dust from our homes, some of it can linger for years. As a result, dust serves as a reservoir for both old and current pesticides. Banned pesticides, often highly persistent, can still be found in topsoil and water, while even less persistent pesticides approved for agricultural use may accumulate indoors. Some pesticides break down when exposed to sunlight, but inside homes, they endure much longer due to the absence of UV light. 

How does indoor dust lead to uptake of pesticides? 

When dust particles are very small, they may become airborne and be inhaled. This depends on the type of floor and cleaning habits. Usually, dust stays on the floor, but when inhabitants move around, including when children play and pets run around the house, dust can become airborne through resuspension. However, even when this happens only a small fraction is inhaled by us.  

A more important route of entry is direct contact with dusty surfaces followed by hand-to-mouth contact. This type of indirect exposure is known to contribute to uptake of many contaminants, including pesticide residues. In a study in the Netherlands, a metabolite of carbendazim observed in urine of adults could be linked to traces of this fungicide in hand wipes. This is more likely to occur in young children, particularly crawling toddlers and until they are old enough to fully follow hand hygiene recommendations. One study found traces of pesticides in a small number of nappies (diapers). The origin of these pesticides could not be verified but indoor dust and food intake may have contributed.  

Infants and young children may be more at risk of pesticide exposure through indoor house dust due to increased hand-mouth contact. 

Is hand-to-mouth contact considered a risk for pesticide uptake via indoor dust? 

In national and EU policy, the risk of ingestion of residues from environmental exposures is considered as contributing to pesticide intake. Often a relatively high contribution from ingestion is assumed in risk calculations, especially for children. This leads to a so called ‘conservative’ estimation of the risk. There is not much evidence for dust ingested e.g., by children in different age groups. Recently, the Dust Ingestion Children Study (DIRT) started with funding from the Environmental Protection Agency (EPA) to study how hand-to-mouth behaviour in children translates to ingestion. 

What can we do to prevent exposure to pesticides in our homes?  

Key recommendations for avoiding pesticide exposure while indoors

Pesticide residues can be taken home with dirt under your shoes. This dirt may contain biological and chemical contaminants including pesticide residues. To avoid this source of contamination, it is suggested to leave shoes outside or at the door when entering your home. 

When you buy products that may contain pesticides, doublecheck the label for any hazard symbols and sentences. If you see a warning which suggests calling a doctor in case of an emergency (e.g., if the product is ingested), consider whether you need to use it, particularly if you have small children at home.  

Many veterinary drugs for pets are pesticides that may be toxic to humans. Once pets are treated with a flea repellent collar or oil, this may become a source of contamination of your home. Direct unprotected contact with the fur of recently treated pets may cause transfer from pet to human. 

Do not cut ornamental plants and cut flowers on the unprotected kitchen bench (where you also prepare your food). Put on gloves and carefully clean the surface with a wet towel afterwards. Before preparing food, remember to wash your hands. 

This article was prepared by Paul Scheepers and Hans Mol. Infographics were designed by Charlotte-Anne Chivers. 

Any questions? Get in touch: This email address is being protected from spambots. You need JavaScript enabled to view it.