I have become interested in raising urban chickens as part of my strategy for decoupling myself from the breaking system of the “official” global economy while living more sustainably. Thus I recently found myself at an urban chicken-keeping class which covered various aspects of the subject, including building backyard chicken coops. During the class, one student mentioned a rather disturbing article that was published in the Portland Tribune on 26 March, titled, “Chickens Eating Lead Not So 'Sustainable.'”
It seems that this article is a response to the explosive popularity of the “urban chicken-keeping movement” in our fair city, and is a criticism of that trend. The author, Tamara Rubin, stated that there is a high risk of lead contamination of the soil of most Portland home lots, due to the lead paint that was used on homes built or painted prior to 1978. She also stated that it takes only two grams of lead dust to heavily contaminate an area the size of a football field. She asserted that chickens on farms are typically less likely to ingest lead, due to the non-lead-based paint used on barns and farms, as well as stating that “most free-range farm chickens and eggs are therefore lead-free.” After giving a few short, general suggestions for testing soil and siting a chicken coop, she concluded by suggesting that the better alternative to backyard chickens is to “[buy] locally farmed, organic, free-range eggs from the store and don't risk inadvertently poisoning your own children in the name of personal sustainability.”
This article hooked my interest, though perhaps not in the way that Ms. Rubin had intended. My interest is always piqued when I hear people warning me or other ordinary citizens away from specific steps toward self-sufficiency. My response is always to ask, “What's really going on here? Is what I'm hearing true? Even if it is true, is it the whole story? Why am I being told these things – especially now?” It was with these questions in mind that I began to study the issue of lead soil contamination in urban areas. This is what I found:
Is It True?
It is a fact that many older urban neighborhoods in the U.S. have soil that is contaminated by lead. The sources of contamination are lead compounds from automobile exhaust and industrial processes, and lead paint on older buildings. The lead from car exhaust was generated by the burning of leaded gasolines, which were gradually phased out in the U.S., starting in 1973 and ending with a complete ban of lead as a component of automotive gasoline in 1996. However, leaded gasoline is still allowed in aircraft, off-road vehicles and farm equipment. The sale of lead paint for residential use was banned in the U.S. in 1978.
Because of the high concentration of heavy industry and car traffic in older inner cities over time, soil lead levels have built up to very high values in these places. The United States Environmental Protection Agency standard sets a maximum “safe” soil lead level of 400 parts per million (PPM) in areas where children are likely to play, and 1,200 ppm elsewhere. As a reference, lead levels in virgin, uncontaminated soil range from 20 to 50 ppm. In cities such as New Orleans, Boston, Detroit and Philadelphia, soil lead levels of nearly 2,000 ppm can be found.
These heavily polluted areas are where poor and ethnic minority populations have historically been concentrated. The small children of these neighborhoods absorb lead via breathing dust and windblown dirt from bare lots, or by ingesting dirt. They frequently suffer central nervous system disturbances as their blood lead levels build to very high values relative to the general population. The children of some of these cities have rates of chronic lead poisoning that are ten times higher than rates of children in affluent suburban neighborhoods.
The lead contamination problems found in older American inner cities is greatly amplified in the cities of the developing world, where environmental and health regulations are much more lax than in the U.S., and where large multinational corporations have moved most of their dirtiest manufacturing operations as a result. The environmental damage wrought by lead pollution prompted this quote from Caltech geochemist Clair C. Patterson: “Sometime in the near future it probably will be shown that the older urban areas of the United States have been rendered more or less uninhabitable by the millions of tons of poisonous industrial lead residues that have accumulated in cities during the past century.” If this is true of the United States, it is true in spades of many places in China, India, South America and other places of outsourced manufacturing.
Lead And Urban Agriculture
Is there a danger then to those who raise their own food in their own backyards? Not as much as one might think. Many studies of this subject have been performed by many groups, including U.S. Government scientists, local universities, local non-profit food security and urban gardening groups, and public-private partnerships between two or more of these agencies. In addition, studies have been performed by NGO's and governments of other nations where lead and heavy-metal soil pollution is a problem. These groups have discovered that lead is not readily absorbed by many plants, nor is it readily concentrated in their tissues to a significant extent. (There are some notable exceptions, however.)
A 2003 study titled, “Lead Levels Of Edibles Grown In Contaminated Residential Soils: A Field Survey,” by Northwestern University, found that those plants that in any way took up or concentrated lead in their tissues did so in their roots first and foremost. Thus, root vegetables such as carrots or onions might absorb between 10 and 21 ppm from growing in highly contaminated soil. Plants were less likely to concentrate lead in their shoots or leaves, although some leafy vegetables like mint had leaf lead levels as high as 60 ppm. Lastly, the fruit portion of fruiting vegetables like corn, beans, grapes and other varieties was least likely to absorb or concentrate any lead. Mitigation of risk from eating these vegetables was easily handled by thorough washing with soap and water. In addition, the 2005 study “Sources, Sinks and Exposure Pathways of Lead In Urban Garden Soil” by Wellesley College concluded that a small child's standard serving of garden vegetables would contribute no more than 10 to 25 percent of the lead found in that child's standard daily portion of tap water.
Then What About Urban Livestock? (Specifically, Chickens)
I was only able to find two studies that directly examined lead uptake and concentration in tissues of chickens. One study, “Lead Contamination of Chicken Eggs And Tissues From A Small Farm Flock,” was cited by Tamara Rubin on her website about lead poisoning, and dealt with chickens that had actually eaten chips of lead paint from an old farm building. While the report states that lead tissue concentrations rose as high as 1,360 parts per billion for the livers of these chickens, concentrations in the eggs of these chickens rose no higher than 450 parts per billion. This study did not analyze the uptake of lead by chickens from polluted soil.
The other study is titled, “The Content of Cadmium And Lead In Muscle And Liver Of Laying Hens Housed In A Copper Industry Region,” and was published by the Agricultural University of Wroclaw, Poland in 2005. This study tracked the lead uptake of two sample groups of hens raised in a region that had formerly been mined for copper, with resulting heavy metal contamination of the soil. This study found that free-range hens and their eggs were likely to have higher concentrations of lead and other toxic heavy metals than their caged counterparts. The weakness of this study is that measurements of soil metal levels were not included, nor were they correlated with the locations of the flocks studied. Therefore, it is not possible from this study to plot the relationship between specific levels of soil and environmental heavy metal pollution and heavy metal blood and tissue levels in chickens raised in this environment.
These studies do indeed show a correlation between environmental sources of lead and increased concentration of lead in poultry tissue. However, these sources do not show the correlation as clearly as it should be shown, especially for lead uptake by poultry on contaminated soil such as is found in urban environments.
There is one other thing to mention, namely that even on regular farms, animals and poultry are being exposed to heavy metal poisoning through exposure to pesticides and inorganic fertilizers. Being on a farm is not necessarily safer in this regard.
Remedies For The Urban Homestead (The Other Side Of The Story)
When one reads Tamara Rubin's writings, as well as the sources I have cited above, one can get the impression that urban gardening and self-sufficiency is scary and dangerous, and that one is better off continuing to rely on the official food system. However, such a conclusion ignores several facts. First, non-profit urban gardening groups and scientists from universities have studied strategies for making urban gardening safe even where soil is contaminated. Northwestern University has published the following recommendations for urban gardeners:
Survey the property to determine the potential lead hazards, extent of the contamination and location of high-risk areas.
Plan to locate fruit and vegetable gardens away from buildings, especially if peeling paint is evident and sites where sludge with heavy metals was applied.
Analyze lead concentration in soil samples from areas where vegetable gardens exist or are planned.
Do not grow food crops in a soil that is contaminated to levels greater than 400 ppm. Instead, use either containers or construct raised beds, with a semi-permeable barrier between the clean and contaminated soil.
Where container or raised bed gardening is not possible, fruiting crops should be grown.
Root vegetables, leafy greens and herbs should not be planted in contaminated soils.
Test new topsoil before using it and annually retest the garden soil to monitor for recontamination.
Do not use plants grown in contaminated soils for compost.
Use mulch or a weed tarp in garden beds to reduce the potential for aerial soil dust deposition or soil splash up on crops.
Others have studied the effect of adding various soil amendments to reduce soil lead bioavailability. One such study, conducted by Hangzhou University in China, discovered that adding phosphorus to lead-contaminated soil bound the lead and made it insoluble, thus less able to be absorbed by plants. Other studies have shown that adding raising soil pH or adding compost and manure to contaminated soil reduces the bioavailability of lead. Lastly, there are agencies who are studying phytoremediation techniques, where specially selected plants are used to draw lead out of contaminated soil in order to reduce total soil lead concentrations. While the other techniques have documented success, phytoremediation is still in an early, experimental stage. And as for chickens, there are several very simple strategies that can be employed in the building of their coops and runs to keep them from coming into contact with contaminated soil.
But before anyone rushes out to secure remedies for soil contamination, the first step is to get your soil tested by a reputable laboratory. It may be that you live in an area that is not heavily polluted.
Conclusion: Bustin' Loose From The System
Having examined the evidence behind Ms. Rubin's article, I believe that she does raise some legitimate concerns regarding lead contamination of urban soils. However, I disagree with the tone of her article, because it forces ordinary, average people of small means into a corner. These are the people who are being squeezed and bruised by their continued reliance on the breaking system known as the official economy. Last year, most of them found it increasingly hard to afford food and fuel as resource shortages led to skyrocketing prices. Most of them even now are being crushed by the weight of unsustainable debt. Very soon they will be squeezed yet again by rising food prices. Midst all of this, they are losing their jobs at a terrifying rate.
What shall we say to such people? “Don't garden; don't raise urban livestock, don't try to be self-sufficient; it's too dangerous”? Shall we tell people that they can only get their food from the store? Shall we pass laws making self-sufficiency illegal? That will go over about as well as a lead chicken. We can't not garden; we can't not keep urban chickens; we can't not learn self-sufficiency. We have to pursue these things. Rather than trying to scare people away from self-sufficiency, let's work on fixing that which has become so broken, while going after the people who did the breaking in the first place.
I'd have been much happier with Ms. Rubin's article if she had mentioned the public/private partnerships between Government and University researchers and urban food security non-profit groups to find remedies for lead soil contamination. I'd have been much happier if she had suggested pressuring the government to make urban polluters clean up urban neighborhoods instead of trying to scare people away from raising backyard chickens. The truth is that the city is where most of us will take our stand, where we will rise or fall in our efforts to carve out a meaningful life to hand down to our descendants amid the crises now converging upon us. We can't all run away to the farm, nor can we continue to rely on a breaking system. As Bruce Sterling said, “The ruins of the unsustainable are the 21st Century's frontier.” We're starting to live in those ruins now. That's where the new pioneers will make their stand. Whatever's broken, it will be up to them to make it work. There is no other choice.
“Field Demonstration of Reduction of Lead Availability in Soil And Cabbage (Brassica Chinensis L.) Contaminated By Mining Tailings Using Phosphorus Fertilizers,” Journal of Zhejiang University Science, 2006, http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1361759
“Sources, Sinks, And Exposure Pathways of Lead In Urban Garden Soil,” Journal of Environmental Quality, 27 October 2006, http://jeq.scijournals.org/cgi/content/full/35/6/2066
“Lead In The Home Garden And Urban Soil Environment,” University of Minnesota, 2002, http://www.extension.umn.edu/distribution/horticulture/DG2543.html
A Resource Guide: The Phytoremediation of Lead in Urban, Residential Soils, Northwestern University, http://www.civil.northwestern.edu/EHE/HTML_KAG/Kimweb/MEOP/INDEX.HTM
Urban Gardens: Lead Exposure, Recontamination Mechanisms, and Implications For Remediation Design, Department of Geosciences, Wellesley College, Wellesley, MA, July 2008 http://www.ncbi.nlm.nih.gov/pubmed/18456252
Greennet Chicago, Chicago's Greening Network, Publications Page, http://www.greennetchicago.org/soil_contamination.html
The Annual Conference On Soils, Sediments, Water And Energy (Formerly known as the Annual Conference On Contaminated Soils), http://www.umasssoils.com/
“City Soil Lead Exposure Maps,” http://urbanleadpoisoning.com/maps.html
“Lead In Soil,” Lead's Urban Legacy, Tulane University,
“Lead for Car Batteries Poisons An African Town,” MSNBC, 4 January 2009, http://www.msnbc.msn.com/id/28484477/
“Lead Contamination of Chicken Eggs And Tissues From A Small Farm Flock,” Journal of Veterinary Diagnostic Investigation, 2003, http://jvdi.org/cgi/content/abstract/15/5/418