Eco Living
Growing Vegetables? Here's How to Check Lead Levels in Your Soil
Lead poisoning is not a long-gone disease but a present-day risk and many Aussie garden soils exceed the 'safe' cut-off
When most people think of lead poisoning, we usually conjure up centuries-old embodiments of this potentially fatal and most toxic of states. The great nineteenth-century writer Charles Dickens described the frightening fate of a woman who worked in the lead mills in ‘A Small Star in the East’. And as far back as the second century BC, the Greek physician Pedanius Dioscorides was said to observe that “Lead makes the mind give way”. However, researchers at Macquarie University in Sydney have conducted a nation-wide study of metal contaminants in Australian garden soils and the results – which are enough to make urban gardeners’ blood run cold – belie the notion that lead poisoning is a thing of the past.
“The general public remains under-informed about the potential risks of exposure from legacy contaminants in their home garden environment,” Professor Taylor and his fellow researchers emphasise in a paper released in 2016. “Despite a range of industrial metals being present in garden soils, lead is typically the metal of most concern due to its toxicity, persistence and abundance in the urban environment.”
In fact, over 40 per cent of domestic soils sampled in Sydney exceeded the national guideline for what is deemed to be ‘safe’ levels of lead. This percentage would be even higher if Australia followed in the footsteps of several other countries and states that have reduced their guidelines, which is the case in California, USA, where the recommended ‘safe’ cut-off for lead levels in residential soils was lowered to less than 100 mg/kg. Strictly speaking, there is nothing safe about coming into contact with any concentration of lead.
“The majority of population IQ points are lost from lead exposure below the current United States and Australian acceptable maximum blood lead level of five micrograms per decilitre (5 µg/dL),” the paper states. As well as the deleterious effects caused by low-level exposure to lead, extreme cases also exist. In 2003, a Labrador retriever died and three young children were immediately hospitalised with lead poisoning in New Orleans, USA, after lead-based paint on a home’s exterior walls was improperly sanded off and not safely contained.
Metal contaminants can crouch hidden in soil for hundreds of years and the increased industry over the course of the last century – especially in built-up and inner-city areas – has seen these contaminants accumulate. As predicted, Taylor and his research team found that soils with the greatest concentrations of lead levels were located in older suburbs with high traffic density. Gardens with the lowest lead levels were from newer suburbs with reduced traffic density, which echoes findings from numerous other studies around the world.
If you live in an Australian city, you join the ranks of 89 per cent of the population who live in metropolitan areas. Approximately 48 per cent of households in these areas try their hand at growing some form of edible produce, which puts vast numbers of the population at risk of being exposed to unhealthy levels of lead.
If you live in an Australian city, you join the ranks of 89 per cent of the population who live in metropolitan areas. Approximately 48 per cent of households in these areas try their hand at growing some form of edible produce, which puts vast numbers of the population at risk of being exposed to unhealthy levels of lead.
In Sydney, the inner west – a swathe of suburbs located to the immediate west of the CBD – recorded some of the most elevated lead concentrations due to the area’s early development and industry, busy roads where formerly leaded petrol accounted for a massive increase in concentrations, and because of the district’s medium-high density housing where lead-based paints were ubiquitous prior to the 1970s before they were banned.
“The dominant source of soil lead for older painted homes is leaded paint, most likely a function of its early use, combined with a longer time period for deterioration of painted surfaces and deposition into adjacent soil. However, improper removal of these paints by blasting, sanding and scraping can expedite generation of lead-rich dust particles that have been demonstrated to contaminate nearby homes,” says Professor Taylor.
“This could explain why a few non-painted homes had abnormally high soil lead concentrations; for example a 70-year-old double brick (unpainted exterior) Marrickville home had soil lead up to 3,220 mg/kg.”
“This could explain why a few non-painted homes had abnormally high soil lead concentrations; for example a 70-year-old double brick (unpainted exterior) Marrickville home had soil lead up to 3,220 mg/kg.”
As well as lead levels differing drastically from region to region across Australia, the lead concentrations within individual properties varied significantly as well. The drip line of older homes represented the most common culprit of elevated lead levels, especially homes that were painted prior to the 1970s. “Urban gardeners who grow vegetables in plots beneath the drip lines of their house, are likely to be doing so in contaminated soil,” Professor Taylor says.
This can be particularly problematic for green thumbs who enjoy a spot of veggie gardening in urban homes and may inadvertently be exposing themselves to high lead levels in garden soil and the food they harvest from it. It can also be downright dangerous, especially for children who are more susceptible to the permanent and even potentially deadly effects of lead when exposed to high levels.
The early twentieth century saw scores of nations recognise the disastrous health risks of lead amid its former use in petrol and household paints and, thankfully, by the 1970s both were largely manufactured lead-free. But if your home hails from before this time – regardless of whether it’s painted or unpainted – and if you live in an older suburb, there’s a chance that the lead levels in your soil could exceed the 300 mg/kg guideline for domestic residences in Australia.
If you’re casting a worried eye across the produce growing in your garden, feel a mounting anxiety about your children playing on the lawn or are growing anxious for your beloved pooch digging in your garden, fret not. The VegeSafe program is still operating and researchers invite participants to send in soil samples, taken from different points on their property, to be tested for metal contaminants.
You’ll usually receive a detailed breakdown of the results from each sample in around three to five weeks, along with advice on what to do next and how you can correct your soil’s lead levels. Many participants have replaced their garden soil either partially or completely, reduced dust-borne lead particles from their soil by mulching or covering the area with lawn, or relocated their veggie patch to planters, raised garden beds or other areas around home. Some participants have even contacted trained professionals who specialise in safely removing lead-based paint to avoid further contamination.
Regardless of your home or suburb’s history, it’s worth getting your soil tested to be on the safe side. Until then, it could be a good time to bust out a window box or fill a planter with good quality potting mix and your favourite edibles so you can keep gardening, keep harvesting and reap the rewards feeling reassured.
Tell us
Have you had lead levels tested at your home? Share your experiences in the comments below, send this story to people you think could be affected and like or bookmark this article if you found it helpful.
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To find out how to send in soil samples for testing, visit VegeSafe
Tell us
Have you had lead levels tested at your home? Share your experiences in the comments below, send this story to people you think could be affected and like or bookmark this article if you found it helpful.
More
To find out how to send in soil samples for testing, visit VegeSafe
In Australia, the guideline for lead levels in domestic residences’ soil is 300 milligrams per kilogram (or 300 mg/kg). Professor Taylor and his team have discovered that of the Sydney residences they have tested so far, the average concentration of lead in households’ garden soil is 415 mg/kg and the highest lead level recorded was over 6,000 mg/kg.