Tool Box Talks on Protection Against Toxin Containing Plants

The dangers from the handling of toxin containing plants is very real for the compost operative.

To the vast majority of composters the green waste coming into their sites is just that green waste. It is considered to have originated from the publics gardens and flower boxes. It is just going to be grass cuttings, hedge trimmings, weeds and the odd unwanted perennial.

This is true the majority of time, but add in that waste is also taken from commercial sources and that the public are not as vigilant or as knowledgeable as the industry would like them to be? Then there are quite a few more things that are likely to appear in the ‘source segregated green wastes’ coming on to sites.

I very much doubt that there is an operator who has not been surprised by something in an input load or uttered words similar to ‘that is green waste? Really?’
There have been improvements, over the years but still there is contamination coming to sites with in the loads. It could just be general household waste, drinks bottles, cutlery, rubble, carpets, sofas (it was green and it had come from the gentleman’s garden!), engine blocks, suitcases, the odd lawn mower, plastic garden furniture, the list could go on? Most of these are easy to spot and removed either by picking or screening. There will always be the low risk of needles but the risks, to the operator, are also well known and mechanised methods are used along side manually removing the contamination. It is now common to see operators using cut resistant gloves and litter tongs to remove the smaller pieces of contamination from the input waste and the active composting material.

The one risk that few sites have really taken in to consideration is actually the green waste itself! Yes most will have considered the physical dangers of thorns but nature has spent a lot of time and effort in to also protect itself with some rather potent chemical defences. Who hasn’t been stung by a stinging nettle? When compared to other plants this is a rather poor defence system but when you consider most UK originating plants? They are somewhat benign and if nothing else edible. Not necessarily tasty but they won’t kill you? Some will give you an upset stomach but then you would have to eat quite a few and make a real conscious effort to consume the plant.  So the risk is mostly over looked as you would presume that it is unlikely that site staff are going to be dishing up platefuls of greens sourced from the input loads? Well you would hope so anyway.

The risk is there in a more subtle manor. It is not the physical plant that is the danger it is the toxins within the plants that are most likely to be the danger to the site operators and users of the end material if not processed correctly.

Within the PAS100 HACCP templates it does suggest that the operator takes in to account the risk posed by a short list of toxic plants. These include rhododendron, yew, ragwort and hemlock. As with the rest of the PAS100 templates they are only a starting point and it is for the operator to extend the list as they see fit. Japanese Knot weed is always the species that is most targeted as the one to be vigilant about and quite rightly as an invasive species but the risk to health is negligible. In fact the young shoots can be harvested and eaten like asparagus and have a subtle flavour.

The risk from most of these plants is the sap. And in most cases it has to be ingested or enter through a break in the skin. That is not always the case though as the toxin found in Ragwort can be absorbed through the skin so when ever handling any part of the ragwort plant barrier type gloves should be warn. Examples of other species that pose a risk, but may not be obviously so include Foxglove and Daffodil. Foxglove contains cardiac glycoside digitoxin and digoxin. Extracts of Foxglove were used by William Withering in early medications for heart failure (1785 "An account of the foxglove and some of its medical uses; with practical remarks on the dropsy, and some other diseases"). It was difficult to get the dosing correct as the difference between an ineffective dose and a fatal one is very little. Although vomiting is one of the first symptoms so it takes a very concerted effort to consume enough for a fatal dose if purely consuming the leaves.

Daffodil is a plant that most people are unaware that it is poisonous. All parts the plant contain Alkaloids with the highest concentration in the bulbs. The symptoms seen would include dizziness, diarrhoea, nausea, and pain. Convulsions and death may occur if sufficient quantities have been consumed. Again it could be presumed that staff are not going to be making Daffodil salad. The Alkaloids can be absorbed through uncovered breaks in the skin.

There is another risk to staff and it is not the danger of the ingestion of a toxin but the actual contact with it. Although not fatal contact with Giant Hogweed results in blistering and blindness if the sap comes into contact with the eyes. Giant Hogweed is a non-native of the UK and like so many of the plants now listed in the Wildlife & Countryside Act 1981 schedule Part II, amended, was introduced into the country in the 19th century as an ornamental plant. Operators should also be vigilant for species listed in schedule 9 part II as they are prohibited from acceptance to composting sites and should only be disposed of in the appropriate manor at a landfill site.

Giant Hogweed sap causes phytophotodermatitis, resulting in blisters, long-lasting scars, and—if it comes in contact with eyes—blindness. These serious reactions are due to the furocoumarin derivatives. The dangers are best illustrated by the incident when a walker accidentally came into contact with it on a walk, The effects are felt for around 7 years, from the original contact, as the toxin is only removed as the skin replaces itself over the natural cycle of skin shedding and growth.

The risks are varied and real so it is up to the management of a site to make sure that they have carried out a sufficient Risk Assessment and from this generated a Method Statement for the task of accepting and sorting input loads. This should take into account what species are known to be local and therefore their possibility of being in the inputs to site. Also how the risk of exposures are to be minimised. It is then vital that these are communicated to the staff and records of this kept.   Any, permitted, site should also have a Waste Acceptance Criteria to govern what waste types are acceptable to site and any procedure relating to this and if required the rejection form site. This will then overlap with the PAS100 HACCP and SOP procedures.

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Jul 16
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