Metaldehyde blue slug pellets were for decades the standard consumer garden product for slug and snail control — sold in every garden centre and supermarket in the UK. Metaldehyde works by disrupting the mucus production of molluscs, causing them to desiccate. The pellets are brightly coloured blue and palatable to pets, wildlife, and children. Dogs routinely consumed fallen metaldehyde pellets, causing severe, sometimes fatal neurological toxicity — metaldehyde poisoning was one of the most common pesticide-related veterinary emergencies in the UK. The UK banned metaldehyde slug pellets for outdoor use from March 2022, following years of campaigning over water contamination — metaldehyde is one of the most commonly detected pesticides in UK drinking water catchments and is not effectively removed by standard water treatment. Ferric phosphate (iron phosphate) pellets are the authorised alternative.
Where it's found
Metaldehyde slug pellets are no longer legally authorised for sale in the UK for outdoor use from March 2022. Legacy stocks may remain in garden sheds. The blue pellet format (metaldehyde) was replaced by the brown/grey ferric phosphate pellet format (e.g. Slug Gone, Growing Success Advanced Slug Killer). Metaldehyde is still used in some agricultural settings in other countries and was widely sold in UK garden centres until the ban. Allotment and vegetable garden soil may retain legacy metaldehyde residues from years of application.
Routes of exposure
Oral ingestion is the primary exposure route — metaldehyde pellets are designed to be palatable to molluscs and are equally attractive to dogs, hedgehogs, birds, and young children. A single standard-size slug pellet sachet contains sufficient metaldehyde to cause serious neurological toxicity in a small dog. Children toddling in gardens where pellets have been applied are at ingestion risk. Water contamination — metaldehyde passes through soil into groundwater and surface water catchments with rainfall; it is detected at concentrations above the 0.1 µg/L drinking water standard in multiple UK catchments, though it is not removed by standard water treatment (chlorination and filtration). Dermal contact during pellet application.
Health concerns
Metaldehyde neurotoxicity is severe and rapid in animals — ingestion causes tremors, hypersalivation, hyperthermia, and seizures in dogs within 30–90 minutes; without veterinary treatment, respiratory failure and death can follow. The mechanism involves acetaldehyde release and GABA disruption. In humans, metaldehyde poisoning cases (primarily from accidental ingestion in children and occupational exposure) have caused similar neurological effects including vomiting, ataxia, muscle rigidity, and convulsions. Water contamination is the most significant ongoing exposure concern for the general UK population — metaldehyde cannot be removed by standard water treatment, meaning that contaminated drinking water catchments require expensive advanced treatment to meet the 0.1 µg/L standard.
Evidence
Metaldehyde neurotoxicity in dogs and wildlife is established from veterinary data and clinical case series — this was the primary driver for the UK ban. Human toxicity from acute metaldehyde ingestion is established from poisoning case reports. Water contamination by metaldehyde at concentrations exceeding the drinking water standard is established from Environment Agency and Drinking Water Inspectorate monitoring data — this was the regulatory driver for the ban alongside wildlife toxicity. The UK ban was grounded in established evidence of unacceptable risk.
Who's most at risk
Dogs and cats in gardens where metaldehyde pellets have been applied — the most acutely at-risk population; metaldehyde poisoning is a veterinary emergency. Young children who may pick up and ingest coloured pellets. Hedgehogs, birds, and other garden wildlife that consume poisoned slugs or pellets directly. People drinking water from catchments with heavy historic metaldehyde use where advanced treatment is not in place.
Regulatory status
RegulationMetaldehyde was banned for outdoor use in the UK from March 2022 under the Plant Protection Products (Sustainable Use) Regulation review. Agricultural indoor use (polytunnels) was temporarily retained but is under review. Ferric phosphate (iron phosphate) slug pellets are the authorised alternative — these degrade to iron and phosphate (plant nutrients) in soil and have no significant toxicity to mammals or birds at field application rates. The EU also withdrew metaldehyde authorisations across member states. Legacy stock use-up periods ended in 2022.
How to reduce your exposure
Replace any remaining metaldehyde pellets with ferric phosphate alternatives (widely available as Growing Success, Slug Gone, and own-brand). Ferric phosphate is equally effective against slugs and is safe for pets, hedgehogs, birds, and children. For non-chemical slug control: copper tape barriers, beer traps, crushed eggshells, wool pellets (which absorb moisture and deter slugs), and encouraging natural predators (hedgehogs, ground beetles, slow worms) are all effective strategies. Night collections by torchlight are highly effective for allotment plots. Check old garden sheds and dispose of any blue metaldehyde pellets at council hazardous waste collection points.
The nutrition connection
Metaldehyde's primary toxicological effect involves acetaldehyde generation and disruption of GABA-ergic inhibitory neurotransmission. GABA is synthesised from glutamate via the action of glutamate decarboxylase, which requires vitamin B6 (pyridoxine) as a cofactor — adequate B6 nutrition supports GABA synthesis and neurological resilience. Magnesium is a co-modulator of GABA receptors — adequate magnesium intake from leafy greens, nuts, and seeds supports inhibitory neurotransmission. The primary risk management action is removal of the product rather than nutritional mitigation; nutritional strategies are supplementary.