[sladefungus]

Hi there
I just started on a plot that was closed for a year due to lead contamination from the water pipe in the allotment tap.  The environmental health say its actually safe to grow things in there now as long as we stay away from the tap.  I am going to enquire about the actual ppm of lead in the soil as ive heard 800 - 1000 ppm is when you should start worrying.  Anyone know anything about growing veg in lead contaminated soil?

[leeky]

Hi there. I would be interested in this too in a round about way concerning lead content in allotment soil alongside motorways. Im not too happy about the close proximity of a plot I may potentially end up with.

Ive done a general search with keywords like "lead content, soil, vegetable, pollution" etc but it probably needs a greater sleuthing ability than I have to drag out some figures.

Hope someone can chime in with relevant info on this worrying topic.


and Welcome!  

[Gwiz]

i personally wouldn`t worry about it.
just think, all water used to be fed around homes in lead pipes, and there is plenty of the "older generation" around still (and a good thing too) you could worry yourself to an early grave thinking of such things.

[WG.]

Anyone know anything about growing veg in lead contaminated soil?

The most serious source of exposure to soil lead is through direct ingestion (eating) of contaminated soil or dust. In general, plants do not absorb or accumulate lead. However, in soils testing high in lead, it is possible for some lead to be taken up. Studies have shown that lead does not readily accumulate in the fruiting parts of vegetable and fruit crops (e.g., corn, beans, squash, tomatoes, strawberries, apples). Higher concentrations are more likely to be found in leafy vegetables (e.g., lettuce) and on the surface of root crops (e.g., carrots).

Since plants do not take up large quantities of soil lead, the lead levels in soil considered safe for plants will be much higher than soil lead levels where eating of soil is a concern (pica). Generally, it has been considered safe to use garden produce grown in soils with total lead levels less than 300 ppm. The risk of lead poisoning through the food chain increases as the soil lead level rises above this concentration. Even at soil levels above 300 ppm, most of the risk is from lead contaminated soil or dust deposits on the plants rather than of lead by the plant.

Given that the River Clyde has a tributary rising near Leadhills in Lanarkshire, then I figure your water supply would be more of a concern.  

[leeky]

http://www.gardenorganic.org.uk/factsheets/gg2.php


Lead and the Gardener
Gardeners and their families are at risk if they grow food in a lead polluted environment. The information collected here draws on research done on lead in soils and lead contamination of food crops, giving recommendations for choice of crop, cultivation practices and careful food preparation that will minimise the risks involved.

Lead in our environment
Lead is a serious pollutant of our environment. Most of it (80%) comes from car exhaust emissions but it can also be released as a by-product of industrial processes. Other sources include residues of lead paint, old lead water pipes, contaminated sewage sludge used as a fertiliser and the use of lead arsenate compounds in orchards. The burning of tyres, soldered tin cans and painted wood also releases lead.

Lead is emitted into the air as particles - the smaller ones remain airborne. We breathe them in; others fall to the ground, polluting soil and dust or settling on trees and plants. Of those we inhale, only the tiniest particles reach the lungs; the remainder are filtered by our nasal passages, but from there get into our saliva and tend to be swallowed.

The majority of the lead we take into our bodies enters through our digestive system, mostly as a result of contaminated food and water. Small children are most vulnerable as they are highly sensitive to lead and also take in lead-contaminated dust and soil licked from their fingers whilst playing.

Low levels of lead (10-20ppm in dry soil) do occur naturally in soils but this is tightly bound and not available to plants. In the industrial world many of our soils already have elevated lead levels. In urban areas or near busy roads, lead particles from the air accumulate in the top 10-20 cm (4-8 in.) of soil, sometimes raising the lead content to hazardous levels (eg. 200-600mg/Kg available lead in central London soils). This has serious implications for gardeners.

Fortunately, in recent years, lead levels in the air have been reduced through the introduction of lead free petrol, a strategy encouraged and supported by increased public awareness of the dangers of lead. Unfortunately, because lead persists in the soil for thousands of years, we now have to live with a legacy of high lead levels in soils that have been polluted.

Why is lead a problem?
Lead is a metal that is toxic to the human body, acting as both a general poison and a nerve poison. Children are particularly at risk: lead interferes with their vitamin D production, and a low level of lead in the environment has been shown to result in impaired mental development in babies and children.

Despite Government/EU attempts to establish safety standards, it is questionable whether there can be a truly "safe" level of exposure to lead because it accumulates in the body and can exert slow, long term effects.

What are the risks from home-grown produce?
The major risk is not that plants will take up high levels of lead through their roots. Plants do not need lead and most species have highly effective natural barriers in their roots to prevent it entering the plant, even when lead soil levels are high as a result of pollution.

Serious lead pollution of vegetables is a problem because of surface contamination. This occurs when lead particles in the air settle on leaves and fruit and become bound to the surface so that they are not readily washed off, and when lead-rich soil adheres to roots and/or splashes onto the crop. At very high lead levels (over 600mg/Kg soil), lead can become toxic to plants and inhibit growth.

What research has shown

Vegetables with a high proportion of the edible part exposed, eg. lettuce and spinach, can accumulate substantial amounts of lead particles from the air, or from soil splashed onto them.
Cabbages grown in urban areas showed highest lead levels in outer leaves, more than three times the level for inner leaves; contamination was also significantly greater nearer to roads.
Root crops such as carrots and swedes developing in contact with contaminated soil will tend to accumulate lead in their skins. This has also been shown for potatoes.
Fruit such as blackberries and raspberries pick up high levels of lead from the air because of their shape - which is particularly efficient at catching lead particles. Blackberries growing alongside busy roads should definitely be avoided as they can pose a serious health hazard.
Onions do not appear to suffer from lead contamination and can be regarded as a safe crop to grow. This would not apply to spring onions as the leaves are consumed and these could pick up lead particles from the air.
What level of lead is acceptable?
There is no single accepted figure for an upper "safe" limit for lead in agricultural or garden soil. The following list illustrates the range:

Department of the Environment 500mg/Kg of dry soil
EU 300mg/Kg of dry soil
Campaign for Lead Free Air 169mg/Kg of dry soil  
Soil Association Organic Standards 100mg/Kg of dry soil  


In our opinion, you should take special care if growing food crops in any soil with a lead content close to or above 100mg/Kg. Where lead levels are as high as 300-500mg/Kg soil, growing food crops is probably not advisable and it would be unwise to let children play on such soil.

If you are concerned that your soil or produce may be contaminated with lead, get it checked by your local Environmental Health Department.

Alternatively, the Wessex Environmental Consultancy, Bath College of Higher Education, Newton Park, Bath, BA2 9BN (tel: 01225 873701) specialises in soil analysis for lead pollution, and will give advice.

[Zak the Rabbit]

500mg is a huge amount, thats half a gram in a kg, so i just wouldnt worry about it, just stay away from the immediate vicinity of the old pipe.

I used to work with lead (its quite common in ammunition) and on ranges where there was quite a bit of lead in the air and ground, and ive also hand smelted the stuff to recycle, and its not caused me any problems,


nnnneeeerrr, neerrr, ne, not affected me at all :shock:  :?  

[leeky]

[Penny22]

THe UK Environment Agency has published Soil Guideline Values for Lead.  The guideline for lead in allotments is 450mg/kg, dry weight soil, based on a child (children are more susceptible to contamination due to their lower body weights).  (The Defra 500mg/kg value provided in the recent listing was withdrawn by Defra as the Environment Agency guidelines are the most recent for the UK).  The local authorities are responsible for identifying contaminated land in their area and ensuring that where there is a risk to human health or the environment the land is 'cleaned' up.  

The values provided by the Environment Agency are guidelines only, so that if the soil concentration is below this amount there is no risk to human health.  If it is above it does not mean that there is a human health risk, further investigation would be required to determine this.

[moz]

With the dry weight figure I not sure if that relates to what is left after a sample has been baked - therefore getting rid of moisture and anything that burns off (with lead being one of the things that would be remaining). I think remember hearing something about this sort of test in he past in a university chemistry lecture - but that was a long time ago and I was possible/probably asleep or hungover  :?  

As for what I would do in your predicament, Im not sure.

cheers,

[Penny22]

With the dry weight figure I not sure if that relates to what is left after a sample has been baked - therefore getting rid of moisture and anything that burns off (with lead being one of the things that would be remaining). I think remember hearing something about this sort of test in he past in a university chemistry lecture - but that was a long time ago and I was possible/probably asleep or hungover  :?  

As for what I would do in your predicament, Im not sure.

cheers,

Dry weight refers to the soil weight when moisture has been removed.  If I was in the same predicament I would contact the Local Authority, as they are the regulator for the contaminated land legislation and would be able to provide advise on whether they consider the site to be of risk to health.

[sladefungus]

yeah i emailed the environment department of the council and used a few scientific words and questions in the email (im a scientist) and was sent the entire 30 page report with maps of sampling points and levels of other metals like copper and zinc, the pH and trace minerals.  even a history of the land for the past 150 years.  makes an interesting read especially when i found out my plot had the lowest levels of lead in the whole allotment - well below any unsafe levels .  I guess the guy who had the plot before me used only rainwater on it.

[Penny22]

Thats great news   , I'm a scientist too!

[ytyynycefn]

Thats great news   , I'm a scientist too!

I used to be, but I'm better now  :twisted: