• Pesticide-Free Cambridge

Helping Cambridge schools to go pesticide-free, & we don't mean just herbicides

Updated: Mar 7

As well as working with City and County councillors to phase out herbicides on verges, streets and pavements in Cambridge, we're also in constructive dialogue with local schools to help them go pesticide-free in the interests of the planet as well as children's health. As the council comes under increased pressure to ditch herbicides in public urban spaces, it makes no sense that schools continue to use them. We've discovered that the vast majority of Cambridge schools are indeed using glyphosate-based herbicides in their grounds. As well as destroying valuable grasses and wild flowers essential for biodiversity, glyphosate-based herbicides have a devastating impact on wild animals and insects that we desperately need to heal our entwined biodiversity and climate change crises. Recent research shows that trying to tackle our climate emergency is futile without first healing the planet through the restoration of nature and biodiversity.(1)

Glyphosate has also been shown to be implicated in a range of short and long-term medical conditions, with increased impacts on children's developing brains (more on which below). Even more worryingly, nearly as many schools also use a dizzying array of synthetic insecticides both inside and outside of the classroom to treat insects that include ants, wasps, flies, fleas, carpet beetles and even ladybirds and bees. It's important to stress that the distinction here is not just between herbicides and insecticides, but also between plant-based and estates/facilities-based pesticide use. We consider it to be hugely problematic that current biodiversity and health-oriented discourse about urban pesticide use tends to focus solely on the former applications, with the latter being more or less completely ignored. We should be just as, if not more, concerned about the health risks of such applications as we are for plant-based pesticide use, while the impacts of these insecticide groups on biodiversity are also just as significant as they are for the ironically named 'plant-protection' chemicals of the kind sold regularly in gardening centres. This is largely because boundaries between indoor/outdoor, or plant/ non-plant applications are very porous, but also because pesticides by virtue of their high volatility, rarely stay in their intended application point.

The inclusion of ladybirds and bees in the list of insects treated by pesticides in Cambridge schools is particularly depressing, and our view is that schools could be incorporating such insect visitations into their teaching curricula about nature and ecology rather than poisoning them in ways that not only threaten already diminished biodiversity but also created highly toxic environments for their pupils.

The most commonly used insecticide group reported to us are pyrethroid or carbamate-based insecticide powders for killing ants. These are used both inside and outside the classroom, the latter usually around the outer perimeters of buildings to stop ants from burrowing into the cracks and damaging foundations. Carbamates are powerful nerve agents, notorious as cholinesterase inhibitors that have been implicated in chemical warfare contexts, more on which below. (2)

Ant on a plant (shutterstock image)

Target 'pests' and pesticide use in Cambridge schools: patterns and trends

We have been collating information sent in to us from parents about pesticide use in Cambridge schools over the last 10 years, with nearly 60 individual points of enquiry relating to 17 local schools (11 primary and 6 secondary). In more recent years we've been following up on these records with more formal conversations between PFC and individual schools and Academies, and we are continuing to fill in gaps in coverage in terms of both date-ranges and schools represented with the aim of providing an up-to-date picture of pesticide use in schools today.

Below we summarise briefly some of the information that we have collated in anonymised format for this 10 year period and that relate to four shorter reporting windows across the following four phases:

  • Phase 1: 2011-2013 (27 records for 8 schools): all primary schools

  • Phase 2: 2014-2016 (8 records for 3 schools): 2 primary/1 secondary

  • Phase 3: 2017-2019 (22 records for 8 schools): 2 primary/6 secondary

  • Phase 4: 2020-2021 (9 records for 6 schools): 2 primary/4 secondary

Figure 1 shows the range of target 'pests' from these four reporting windows, with corresponding numbers of reports and school numbers to which they relate. There are reports of routine glyphosate use at all 17 schools across the four phases, apart from one school which for one year in Phase 2, and three years in Phase 3 was using mechanical weed control methods, with one more recent case study like this towards the end of Phase 4 (see 'Progress and Positive Developments' section below). Ant problems were reported at nine out of 17 schools, through a total of 18 reports, with wasps being the next most commonly treated 'pest' through six reports from the same number of schools, with corresponding carbamate and pyrethroid-based insecticides being the poisons of choice for treating such insects.

Figure 1: 'pest' types mentioned across four reporting periods

As shown in Figure 2, there were 27 reports of insecticide use at 13 out of 17 schools in the previous year from the time of enquiry across the four reporting periods. Nine of these reports (at five schools) relate specifically to insecticide powders which, as discussed below, present particular problems in terms of toxicity, volatility and environmental persistence. There were 13 reports from seven schools of routine insecticide treatments and 14 single treatments at 10 schools over at least one year previous to the point of enquiry.

Figure 2: Types of pest control methods mentioned over four reporting periods

As shown in Figure 3, all of the reported insecticides have as their active ingredient either carbamate, a cholinesterase- inhibiting nerve-agent (seven reports from six schools), pyrethroids (eight reports from four schools), or a combination of the two (12 reports from seven schools). Such poisons are most commonly used for ants and wasps, but also for other insects such as fleas, flies, carpet beetles, and even bees and ladybirds. Further, in terms of toxicity and environmental persistence, these chemicals are considerably more problematic than glyphosate and yet barely figure in discourse on pesticides-in-schools.

Figure 3: Active ingredients mentioned across four reporting periods

Figure 4 shows the ratio between indoor and outdoor insecticide applications. 11 out of 27 (48%) reports of insecticide use were applied indoors in either classrooms or halls (10) or kitchen locations (1). However, the most commonly mentioned site of application (59%), especially for ants, was around the outer peripheries of the school building, in cracks at the edges of the building (12) or at the school entrances themselves (3). Such locations, although by definition 'outside' result in considerable indoor cross-contamination due to both footfall and wind-driven drift. Half lives of some of these active ingredients are extremely high in indoor environments which adds to their overall toxicity and impact on developing human nervous systems.

Figure 4: Application location for insecticides mentioned across four reporting periods

Biodiversity impacts of estates/facilities insecticide use

Although much of the above-cited data are anecdotal and there are significant gaps in the available information, it's alarming that such toxic chemicals are being used in schools when extremely effective mechanical alternatives exist, such as the well established method of applying a mixture of bicarbonate of soda and sugar to ant access routes and building cracks.(3) Ants coming into buildings can pose a treat to building stability, so whilst we don't like killing insects and especially ants that perform such crucial ecological roles, it's important that we're able to suggest effective alternatives to schools in such contexts rather than just say 'leave the ants alone' as this is more likely to make people feel that there is no alternative to using poison. That said, less well established colonies can sometimes be encouraged to leave through non destructive deterrents, but these require much more trial and error, something that schools might be less willing to try. Since ants are often more of a problem in older buildings, often calling for repeated insecticide use over many years, new-build schools offer unique opportunities to start from scratch and to plan ahead for integrated pest-control approaches.

Whilst ant powder is generally associated with estates and facilities contexts we have also received reports, although relating more to local businesses and residential contexts rather than to schools, of ant powder being applied in gardens, on pathways and around flower beds to prevent ants from reaching plants, or from nesting in paths or patios. This is completely incomprehensible given that ants are doing no damage in such environments, but rather have been shown to be essential components of healthy soil ecology. Research demonstrates that ants are key soil modifiers , improving soil fertility, increasing plant diversity and acting as crucial 'ecological engineers' to this end.(4)

The use of ant poisons, along with other ironically termed 'plant-protection' chemicals, threatens these and other much maligned species such as wasps and moths that are now known to be just as essential as pollinators as bees.(5) This begs the question of why more attention is not given to insecticides in current non-agricultural pesticide-free campaigns, especially given their prevalence in both indoor and outdoor contexts. Ant powder which is often sold alongside cleaning products in supermarkets may not be applied directly to plants as are glyphosate-based herbicides and other 'gardening' chemicals, but given its potency and volatility, is bound to impact negatively on biodiversity as well as on increasingly threatened arthropod populations just as much, if not more, than herbicides. And even when applied in non-garden contexts, such as inside buildings, around the outer peripheries of buildings and walls, as is the case in so many schools, insecticide powders are easily spread by wind and footfall far beyond the site of application, with high potential for unpredictable and unintended impacts on fragile, non-target insect populations and environments.

Children and insecticides

Moreover, young, developing brains are much more susceptible to the toxic effects of both herbicides and insecticides than their adult counterparts. Research has demonstrated a close link between pesticide exposure and certain cancers, but also chronic neurological disorders such as migraines, ME/CFS, ADHD, autism, as well as DNA alteration and endocrine disruption.(6) Insecticides, in particular, remain active in indoor environments for many many years, meaning that children sitting in classrooms indoors are potentially being exposed to poor air quality and pesticide residues for the duration of their school years.

Given that children spend upwards of six hours a day in classroom settings, it is vital that the air they breathe is clean and free of toxins. Recent campaigns have sought to control the use of agricultural herbicides in the vicinity of residences and schools to reduce the health impact of pesticide ‘drift’. But there is little point in banning pesticide use near schools when schools themselves are directly dousing their premises, both indoors and outside, with equally toxic pesticides. Similarly, recent reports on the impact of air pollution in and around Britain's schools rightly highlights the link between vehicular and agricultural fumes pollution and a range of serious health disorders in children, but unfortunately does not consider at all how urban pesticide use in and around schools is contributing to the problem.(7)

Pesticides are major contributors to biodiversity breakdown, and thus by extension to the climate change emergency also; but they are also central to an emerging public health crisis that should be getting much more attention than they currently do. Given the growing number of people and groups who care about the environment and the wellbeing of the next generation, improvements to the ecological health of the buildings and the micro-environments in which our families live, study and work should be just as relevant for tackling our global planetary health crisis as are the larger-scale national and international mediators of climate change and the destruction of nature.

Progress and Positive Developments

Against this worrying situation, there are several positive approaches to weed and insect control at Cambridge schools for which we have reports. We know of one school that successfully trialed mechanical methods for treating ants including boiling water, and a bicarbonate of soda / sugar mix. The school apparently reported that the latter's efficacy was significantly superior to that achieved by commercial ant powder that they had been using in previous years. We are seeking an update as to whether this approach has been retained in the longer term.

The advantage of this method over synthetic insecticidal topical treatments that poison ants on contact is that the bicarb/sugar mixture is taken back to the nest and by destroying the entire ant population at source, through a series of alkaline/acid combustions, the usual need for constant reapplication is avoided. We can only surmise that the reason that so many schools have to use synthetic poisons so 'routinely' is that such methods are less effective than mechanical means - combined with rigorous structural maintenance and strict hygiene measures - at eliminating the root of invasive 'pest' problems.

Another school reportedly adopted manual weeding for several years during Phases 2 and 3. We are currently seeking an update as to whether herbicide alternatives are still being used at this school. Unfortunately, such positive developments are easily undone as a result of turnaround in student cohort and senior leadership personnel.

We know of three schools which for various reasons were not using, or had no need to use insecticides for at least three years prior to the point of enquiry at various points between Phases 2 and 4. We are seeking an update on all three cases to see if there have been any resultant permanent changes to pest-control policies at these schools.

We were also delighted to learn from another school with which we at Pesticide-Free Cambridge are currently in constructive discussion (Phase 4), that they have now decided to replace routine ant powder treatments with a bicarbonate of soda/sugar trial, and that they are also committed to going herbicide-free across their school grounds. It is very encouraging that they have taken on board our suggestions and that they have had the foresight to acknowledge that insecticides and herbicides in schools need to be tackled together. Moreover, when it comes to deciding which group of insecticides to eliminate first, prioritising ant powder is a no-brainer given its prevalence at so many schools, its excessive toxicity, and the ready availability of cheap and effective alternatives. We are in ongoing discussion about how other commonly treated insects in schools might be dealt with effectively through non toxic and effective means and we are optimistic about the prospect of their eventually going completely pesticide-free, perhaps even representing a UK-first in this regard. Watch this space for updates!

We wish them all this school all the success with this positive new approach and hope that when other schools see what's possible, they will follow suit too. Our hoped-for end result is that all schools will be able, through the application of environmentally-sensitive building and grounds management styles, to set an example to their pupils about what a healthy biodiverse world that restores children's everyday engagement with nature, should look like. This is crucial in light of recent research that highlights children's increasing dislocation from the natural world.(8)

The next steps

We'll be reporting on other developments in our schools campaign over the next few weeks, including our ongoing discussions with both City and County Councillors. We'll also be sharing other suggestions as to how parents and pupils alike can get involved with making Cambridge schools pesticide-free, including an art and poetry challenge.

What can you do to help?

1. Contact your school

  • Get in contact with your school to ask about pesticide use. Different schools keep records on such matters in different ways, with information being held variously by Office staff, theSenior Management Team, Grounds or Estates & Facilities Manager, and often a combination of all three. Some kinds of pest control are carried out by internal staff, others use external contractors. Often there is a combination of the two depending on what's being used. For example, herbicides might be applied by the school grounds manager, whilst many insecticides are applied by an external pest control firm. So in order to get a comprehensive picture you may need to call around, or wait for information to be relayed from one department to another.

  • Ask your school what methods they use to control weeds in their grounds. Ask them to consider using chemical free forms of weed control. Involving children in the manual removal of weeds is a great way to raise awareness in this respect. Or alternatively, to re-examine the notion of what is a ‘weed’, and what is a ‘plant in the wrong place’ and how such plants might be incorporated into children's education about biodiversity and the natural world (see our main website for further reading on this topic:

  • Ask your school what insecticides they have used in the last year both outside and indoors, and what their pest-control policy is should an insect infestation arise. Ask which products have been used, with dates, and details of where such chemicals were used.

  • . Ask your school to consider the use of non toxic forms of insect control. For example, a mixture of bicarbonate of soda and sugar is often much more effective than carbamate or pyrethroid-based insecticide powder for treating ants, without any of the long-lasting impacts on children's brains. Put them in touch with Humane Wildlife Solutions, an award-winning pest control firm that offers UK-wide consultations for how to treat insects and other wildlife in homes, businesses and schools without recourse to toxic pesticides. Other ideas for non-toxic or integrated forms of pest control can be found here.

  • Even if schools are unprepared to stop using pesticides, ask them if they will agree to pre-warn parents about any planned pesticide use, and also to put up signage when herbicides or insecticides have been used so that parents are aware of the situation

2. Sign up for PAN-UK's Pesticide-Free Schools pledge

Access and download resources from PAN-UK’s Pesticide-Free Schools website here and share these details with your school. On their excellent site you’ll find a downloadable leaflet , posters and maps explaining how parents, children and schools can get involved with the campaign to make their schools pesticide free. There are is also a postcard that can be printed out to distribute amongst pupils and parents and to demonstrate objections to pesticides on school premises. Note however that PAN-UK's pesticide-free schools site only looks at glyphosate-based herbicide and does not consider insecticide-use in these environments at all. This is a pity given that insecticides are often tracked indoors on feet, or applied directly inside school buildings, where the absence of rain and sunlight prolongs chemical ‘half life’ considerably. So make sure that if you do ask your school to consider eliminating pesticides from its grounds that you stress that it’s insecticides as well as herbicides that you are concerned about. Our experience so far with pesticides in Cambridge schools suggests that singling out ant powder is a good idea, not only because it's so prevalent and so damaging to biodiversity as well as human health, but also because it's so easy to replace with mechanical means.

3. Get in touch with us

Please contact us if you'd like to check if we already have information about pesticidee-use at your school, or if you'd like to share any progress you have made already with encouraging your school to go pesticide-free.

[JS @ PFC]



(2) Mirjana B. Colovic, Danijela Z. Krstic, Tamara D. Lazarevic-Pasti, Aleksandra M. Bondzic and Vesna M. Vasic, “Acetylcholinesterase Inhibitors: Pharmacology and Toxicology”, Current Neuropharmacology 2013; 11(3) . ; For further reading, see


(4) Farji-Brener AG, Werenkraut V. The effects of ant nests on soil fertility and plant performance: a meta-analysis. J Anim Ecol. 2017 Jul;86(4):866-877. doi: 10.1111/1365-2656.12672. Epub 2017 May 8. PMID: 28369906.



Muhammad Sarwar | Albert Lee (Reviewing Editor) (2016) Indoor risks of pesticide uses are significantly linked to hazards of the family members, Cogent Medicine 3:1, DOI: 10.1080/2331205X.2016.1155373



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