Gardening, Lead Contamination, and Children

The health threat posed by toxic metals was recently brought only too close to home when a group of urban crop raisers discovered a connection between gardening, lead contamination, and children.
By Dr. John Gofman
July/August 1981
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Auto exhaust from leaded gasoline was also once a major source of lead contamination.
BEN BARBER AND MOTHER EARTH NEWS STAFF
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... if we're letting the lead industry getaway with dangerous pollution, we should do something about the lead industry ..."  — Dr. John Gofman

Some 5,000 years ago, the human race smelted the first lead-silver alloys, and thus began soiling its own nest with the heavy metal. In fact, at the high point in their history, the Romans were using so much lead in pots and aqueducts (indeed, the very word "plumbing" comes from the Latin word for lead, plumbum) that the toxic element may well have contributed to the downfall of their empire. Yet in spite of the fact that people have long recognized the health dangers of processing and using lead, we now mine and employ an almost astronomical quantity of the metal. (Compare the 80,000 tons of lead produced each year during Roman times to the 3,000,000 tons produced—annually—today!)

Lead is, in short, omnipresent in modern society (the metal has even polluted the polar icecap), and perhaps that's the reason most of us have seemingly forgotten that it exists. We're constantly exposed to the heavy metal in the form of house paints, industrial emissions, exhaust from automobiles, colored ink in all types of printed publications (even including candy wrappers), ceramic glazes, the solder used to seal food cans, old water pipes ... and more.

But a new groundswell of concern about the dangers of lead contamination is beginning to take hold in our country. And the movement was spawned, ironically, by an investigation of one of the least suspected means of human lead ingestion: gardening.

Now you may well be shocked by the notion that growing one's own food—an activity that's come to be symbolic of wholesome, self-reliant living—can actually be hazardous to human health. But don't get too alarmed. Lead toxicity is a problem only in some gardens and for some people (primarily small children), and as we'll explain, the hazard can be identified and dealt with in those instances. However, there is real cause for concern about all the means by which lead finds its way into your own and your children's lives, especially since many other sources of exposure to the toxic element are likely much more significant than is any that can come from a home vegetable plot.

It was a group of gardeners, though, who recently rekindled public awareness of the lead issue, and it's those same horticulturists—members of an organization of community gardeners in Boston, Massachusetts—who are working hard to educate people about the numerous ways (including crop raising) in which families may be exposed to harmful levels of the metal. The purpose of this article, then, will be to share some of what many such health-conscious people have learned, so you can effectively reduce the sources of exposure to lead in your own life.

The Effects of Lead

Although many of the facts of this complex issue are obscured by controversy or ignorance, no one—not even the most ardent defenders of America's lead industries—would deny that, at high levels of exposure, the element labeled "Pb" is dangerously toxic. Victims of "clinical" lead poisoning (which is also called plumbism) can suffer headaches, nausea, anemia, kidney damage, blindness, hemorrhage, convulsions, coma, and death.

Another undisputed truth is the fact that children under six (including, since lead crosses the placenta, infants still in utero) are far more susceptible to lead poisoning than are adults. Youngsters have high metabolic rates, are at delicate stages of growth, and are often physically close to such sources of lead as old paint chips, contaminated dirt, and auto exhaust. All told, children's bodies can absorb and retain around 40% of the lead that they ingest. Adults however can eliminate all but a small percentage of the element that gets into their systems. Consequently, youngsters are much more likely than adults to develop serious lead poisoning. Of course, men and women employed in lead smelting, storage battery manufacturing, shipbuilding, automotive body painting, printing, deleading, pottery glazing, and other lead-related industries or crafts may—because of the high levels of exposure in such occupations—suffer clinical lead poisoning as well.

But the accepted truths don't tell the whole story of lead intoxication. Recent evidence indicates that even Pb intakes well below established clinical levels can seriously harm children. Youngsters with low-level lead exposure are sometimes afflicted with headaches and abdominal pain or such "lesser" symptoms as irritability, clumsiness, listlessness, and loss of appetite.

And, sadly enough, the organ most easily affected in a growing child is the brain. Dr. Herbert L. Needleman carefully compared the levels of lead in children's teeth (the heavy metal accumulates in teeth and bone) with the same youths' rating by various testing systems and teacher evaluations. (The results were reported in the March 29, 1979 issue of The New England Journal of Medicine.) He discovered that low levels of absorbed lead can decrease a child's attention span, impair his or her auditory and language-processing abilities, promote poor social behavior, and—in a word—reduce the youngster's intelligence.

Worse yet, the brain damage caused in young children by "subclinical" lead poisoning is often irreversible.

Leaded Gardens?

One of the strongest recent efforts to combat the hazards of lead exposure began in 1977, when a few members of the Boston Urban Gardeners (BUG)—an organization dedicated to revitalizing communities and people's lives by means of vegetable growing—became worried that some soil might contain enough lead to endanger small children. The BUG members, along with concerned scientists and public agency representatives, investigated the subject and demanded that their city's public services address the problem. The group's dogged efforts paid off handsomely, too: Boston (and the state of Massachusetts as a whole) now offers soil-lead testing, blood-lead testing, and related health information to all of its residents.

The Boston task force raised the question of whether plants could absorb lead that's present in garden soil. To find the answer, Thomas H. Spittler and William A. Feder cultivated lettuce, beets, carrots, snap beans, and radishes in a carefully controlled greenhouse environment during the winter of 1977-78. They found (and published their findings in "A Study of Soil Contamination and Plant Lead Uptake in Boston Urban Gardens," Communications in Soil Science and Plant Analysis, 1979) "a definite correlation between soil Pb content and plant uptake." The researchers went on to observe that the element tended to concentrate primarily in plant leaves, to a lesser extent in roots, and hardly at all in fruits. (Hence, tomatoes absorb much less lead from soil than do potatoes, which in turn take in less than does spinach.)

More important, though, Spittler and Feder also expressed a possibility that other researchers soon verified: If one's garden soil is so toxic that the plants can absorb a measurably significant amount of lead, the earth itself is more of a health threat to children than are the crops! As research agronomist and heavy-metal expert Rufus L. Chaney put it, "We think we have confirmed that plants don't take up enough lead to matter, as far as its getting into people's diets is concerned. The really big risk is soil ingestion by children." After all, youngsters play in dirt. They're likely to get some on their hands and accidentally ingest contaminated soil in the course of normal hand-to-mouth play, or—in some cases—even develop the habit of deliberately eating soil (and other nonfoods ... a pattern of behavior called "pica").

Essentially, then, gardening in lead-contaminated areas can constitute a health risk to young children (although not, at least so far as we now know, to adults), and this threat comes primarily from the soil itself rather than from the plants per se. (Indeed, more lead is likely to accumulate on the surface of crops—from settled auto exhaust fumes and garden dirt—than will collect inside the vegetables.)

The problem of toxic soil is not a short term one, either. The metal does not tend to percolate down through the ground, but instead settles in the top few inches of earth, where it can remain for centuries.

Where Does It Come From?

And just how does one's garden plot or yard build up a dangerous level of lead to begin with? There are several possible means of contamination, and their relative importance will vary from site to site, but the most likely source of severe lead buildup is house paint. Until 1950, you see, almost all homes were protected with paints that contained dangerous amounts of lead. (In fact, some home coatings used for years after that date—right up to 1971—were formulated with lesser but still significant doses of the metal.) And even though old buildings may have since been repainted, several times, with less toxic coverings, the original lead-based exterior layer can still shed the dangerous element into the soil. Chips of the material may drop off, and rain will—over time—wash some lead down from even nonpeeling walls. Or, worse yet, a lead-painted building may have been burned or demolished years ago on what's now a gardening site.

Lead is deposited in the soil in many other ways, as well. In areas near heavily traveled roads, auto exhaust fumes can contribute an appreciable amount of the toxic substance to the earth. Emissions from factories that use lead in their manufacturing processes can constitute a very significant local Pb source. Even treated sludge can contaminate—rather than fertilize—garden soil.

You may be surprised to know that, contrary to popular myth, lead-sullied soil is not only an urban problem. Rural folks need to be concerned about it too. Any country vegetable plot that's next to—or receives rain runoff from—an old painted house or barn will most likely contain an above-average level of lead. Farm plots, like city gardens, can be located close to frequently traveled roadways or downwind from industrial lead-using factories. On top of that, the ground may have received an extra burden of lead if its owner has—at one time or another—spread wood ashes from painted boards on his or her garden site.

A rural growing plot may also be significantly contaminated if the soil was formerly commercial farm acreage: For many years, lead arsenate was a common ingredient in pesticides (particularly in those insecticides used in orchards).

The Blood Test

As you can see, having lead-contaminated ground can increase the amount of exposure that your children will have to the toxic metal, but remember: Human beings absorb lead from many sources.

Therefore, it's important that concerned parents determine whether or not their youngsters are ingesting and retaining harmful amounts of lead, regardless of the environmental source. Fortunately, there is a way to determine the amount of the dangerous element currently entering any person's system: a blood test.

To get your own or your child's blood checked for lead content, first contact your nearest health department and ask whether it offers this service. (If the agency does so, the testing may well be performed free of charge.) Should the folks there not be equipped to handle this exam, ask them—or your family doctor—who, in your region, does have the capability. One of those parties should be able to find out, take your blood sample, and send it off for testing. If, however, neither your physician nor the health department can locate a blood-lead testing service, write the Department of Health and Human Services, Public Health Service, Center for Disease Control. Someone at that agency will send you the address of the testing center nearest you.

A blood-lead test will be either a fingerstick exam (in which blood is taken from a pricked finger) or a venous test (in which the sample is drawn from a vein in the arm). Both types give an erythrocyte protoporphyrin, or EP, reading. (Protoporphyrin is a substance that accumulates in the bloodstream's erythrocytes—the red blood cells—when excess body lead interferes with normal hemoglobin production. An EP test, then, is a good indicator of the extent to which lead is currently affecting one's body.) EP results are given in micrograms of protoporphyrin per 100 deciliters of blood (mcg/100dl). A reading below 50mcg/100dl is currently considered to be a "normal" EP level, while counts of 50-249 mcg/100dl and 250+mcg/100dl are considered "excessive" and "dangerous", respectively.

The venous blood test measures the blood-lead level as well as an EP count. A level of below 30 micrograms of lead per 100 deciliters of blood is currently considered acceptable. (The Boston Urban Gardeners people warn that it's best to take that "acceptable" designation with a grain of salt, however, since it is now suspected that blood-lead levels as low as 10mcg/100dl may cause some damage to a child!) Readings of 30-49mcg/100dl, 50-69mcg/100dl, and 70+mcg/100dl are officially categorized as "elevated," "excessive," and "dangerous," respectively.

Both types of blood test indicate the level of lead currently circulating through a person's body. The advantage of such readings is that they offer means of gauging change: You can quickly discern how much lead your children are ingesting, then find out, through subsequent tests, whether you've been successful in reducing that toxic intake. The limitation of the exams—on the other hand—is that they don't provide figures for the total amount of previously absorbed lead that may have permanently accumulated in the body.

To insure that your own children are safe from low-level lead intake, you should test youngsters aged six months to three years—and your older offspring, if you live in a high-risk area—once every six months. Most children beyond three years of age require only a yearly checkup.

What to Do

If blood test results indicate that a child of yours has an excessive or dangerous lead level, you should see a doctor for immediate treatment of this serious poisoning problem. If, however, the results indicate no more than a possibly elevated blood-lead count, take measures (such as those described below) to reduce the amount of lead the youngster ingests, and use a series of doctor visits and follow-up blood tests to see how successful your efforts are. According to the Center for Disease Control in Atlanta, the child's blood lead should remain stabilized at a safe level for six months before the parent can feel that he or she is effectively dealing with the problem. (Keep in mind, too, that a youngster's blood-lead level will often fluctuate on a seasonal pattern and tend to be highest during those let's-play-outdoors summer months.)

And, of course, whatever steps you take to reduce the lead in your child's environment, be aware of the possibility of exposure to the metal in your garden's soil, along with the other potential sources of ingestion.

Gardening With Lead 

According to the Boston Urban Gardeners' Julie Stone, you can feel pretty sure that your soil has a high lead level if it's [1] located next to an old painted building, [2] on the site of a former building or dump, or [3] in an area that's heavily contaminated by auto or lead industry exhaust. Should any of the above conditions apply to your garden, it's best—for the safety of young children or any other persons in your household who face high levels of lead exposure in their occupations—to grow all vegetables in containers ... find another, safer gardening site ... or have the topsoil replaced with clean earth. You should also make sure any exposed garden dirt can't become a health hazard by covering it with gravel or with a tough grass such as K-31 fescue.

It's much more difficult to "guesstimate" whether your garden may have an elevated (rather than high) lead level. If the plot is in an area that's not far from an old painted building or is subject to regular smog or some auto exhaust, though, you will probably want to take the following gardening precautions to protect any lead-risk family members:

  • Grow leafy green vegetables and root crops as far as possible from busy roads or older houses.
  • Use fences or tall plantings of sunflowers, morning glories, or dwarf fruit trees to help cut down the amount of airborne lead that reaches your garden.
  • Wash all produce (especially the fruit grown to provide an airborne lead "windbreak") thoroughly before eating and discard the outer leaves of lettuce, cabbage, chard, etc.
  • Peel all root crops before eating them.
  • Enrich the soil with peat moss, compost, or manure. The organic matter will help you raise healthier, more nourishing plants and add uncontaminated growing medium to your soil.
  • Mulch the garden. Aside from helping plants thrive, the covering will keep airborne lead off the soil. (If your garden site is exposed to a lot of poisonous exhaust, discard the mulch at the end of the growing season instead of composting the material or tilling it into the ground to avoid adding the accumulated lead to the garden.)
  • Adjust the soil pH until it's as close to neutral as your crops will tolerate. It's been suggested that a neutral pH will tend to inhibit lead uptake by plants grown in soil with a moderately low level of lead.
  • Add phosphorus to your soil. Lead will often bind to that mineral and form the safe substance, lead phosphate. (In fact, research agronomist Dr. Rufus L. Chaney believes that neutralizing an acidic plot without adding extra phosphorus might even be counter-productive, since the increased alkalinity will tend to render ineffective whatever amounts of the lead-binding element are already in the soil.)

Dirt and Dust

Besides following the foregoing gardening suggestions, a person who's trying to reduce local heavy metal contamination in his or her area should also wage war against the amount of leaded dirt and dust a child may be exposed to while at home or at play. (Such Pb "carriers" frequently are among the major contributors to lead poisoning in children.)

To do so, the members of the Boston Urban Gardeners recommend that you always wash your children's hands before the youngsters eat and after they've been playing in any dirty area; build a sandbox so they'll have a spot to play that doesn't contain contaminated soil; be sure your tots sit at a table when eating outdoors (a couple of boards set on crates will do fine); grow a tough grass ground cover in dusty areas; place old rags or mats over scruff spots such as the earth under swings and at the bottom of slides; and get rid of any paint chips found near buildings. It's also important to keep the interior of your home as dust-free as possible by thoroughly wiping furniture and sweeping and wet mopping floors. In addition, if any member of your family works in a lead-related industry, that person should always shower, shampoo, and change to clean clothes and shoes before coming home.

Diet Can Make a Difference

One of the most positive steps you can take to reduce the amount of lead your children absorb is to make sure the youngsters have healthful diets. Iron and calcium, in particular, are very effective in combating lead retention in the body. Foods high in iron include dried fruits, dark leafy vegetables, and red meat. Dairy products, some nuts, and most vegetables are good sources of calcium.

It may be best, though, to reduce the amount of canned foods your child eats, since the solder used to seal the cans may contain significant amounts of lead. Indeed, according to Dorothy M. Settle and Clair C. Patterson's estimates (in "Lead in Albacore: Guide to Lead Pollution in Americans", Science, March 14, 1980), "Half the lead in the American diet probably originates from lead-soldered cans." So it's actually possible that a person could get more toxic metal from a tinned tomato than from one grown in his or her own lead-contaminated garden!

Fortunately, since Settle and Patterson made their study, many canning companies have started to drastically reduce the amount of lead solder in their containers, so the possibility that leaded cans may contribute significantly to lead accumulation may be fading. Two particular canned foods definitely worth avoiding, though, are citric juices that have stood, opened, in the refrigerator a few days and tinned infant formula. (Aluminum cans may be safe, but we don't recommend them.)

Lead in Pipes

Older homes, and some old municipal water systems, may have lead waterlines, and such pipes can be another source of the toxic element (particularly in regions with soft water). People trying to reduce their family's lead intake should—if their drinking water comes through lead pipes—consume bottled water, use a water treatment unit approved for lead removal by the EPA, or, at the very least, run the tap for a few seconds before drawing any liquid for drinking and cooking purposes. (You should be able to get your water tested for lead content by your local Public Health Service, water pollution control agency, or even a person or organization who does blood-lead testing.)   

Lead Paint

Without a doubt, though, the easiest way for any child to get an extremely high dose of lead is by ingesting lead-based paint. So, besides cleaning up paint chips inside and around your home, you may—if the house was at one time coated with such a paint—want to cover the interior walls with paneling or wallpaper, or remove the toxic coating entirely.

If you decide to get rid of the lead-based paint, be absolutely sure you take all the proper precautions. Don't use a power sander (which would create dangerous dust) or burn the old coating off (which, worse yet, would vaporize the toxic matter). Instead, remove the paint by dry scraping only. Use a drop cloth, wear a respirator, keep the work area and workers clean, change clothes after working, and eat in a separate space. In other words, follow strict sanitary measures. In addition, make absolutely certain that children and pregnant or nursing women stay away from the work area. There have been numerous reported cases of well-intentioned home remodelers who received damaging doses of lead while de-leading their houses.

Soil Testing

One of the most positive lead-control actions any concerned person can take is to help organize a community soil-testing program. There are very few parts of the country right now where an individual can easily get his or her cropping ground tested for lead content ... but that state of affairs can be changed.

The best-known example of a successful community soil-lead testing program is, as you'd imagine, the one in Boston. As BUG's Julie Stone describes it, the folks there were able to convince the extension service and other government agencies to set up soil- and blood-lead testing services, partially because they rallied concerned scientists and agency officials to their cause, but primarily as a result of "a handful of committed individuals who learned never to take no for an answer."

While gathering support from a number of determined people might well be the best way to initiate a lead-testing movement where you live, Linda Roth of the Suffolk County, Massachusetts Agricultural Extension Service advises that you will also have to track down a facility that has the type of (expensive) spectrophotometer that can run accurate soil-lead tests. Linda suggests that you first contact those experienced soil testers, the folks at your county extension service, to see whether they have the needed equipment on hand.

Other places that might be able to provide access to the machine are state agricultural extension programs, university science labs (you could even be fortunate enough to find a graduate student interested in testing soils as part of his or her research work), state health boards, regional labs of the Environmental Protection Agency, state pollution control agencies, and private medical or research labs. Indeed, the Boston Urban Gardeners located one of their first testing facilities at a private laboratory after one of the members read a newspaper article about a researcher who was looking into lead levels in pet foods!

The Big Picture

Evidence of the hazards of lead contamination keeps mounting steadily, but unfortunately, the amount of the toxic element being added to our total environment is also ever on the increase. Conscientious measures to help protect one's own garden soil, family, and community are important, but individual efforts obviously aren't enough to remedy the situation. We all need to take action to meet the problem at its source: that is, to reduce the amount of the toxic metal being spewed throughout our country.

And, as a first step, you should know about some pending government decisions that may cause serious setbacks to much of the progress that has been made in combating environmental lead contamination in the U.S.

[1] The Clean Air Act of 1970 is up for revision this year. This major piece of legislation has helped regulate the amount of airborne particulates, sulfur dioxide, carbon monoxide, hydrocarbons, nitrogen dioxide, ozone, and lead introduced into the environment. There are many interests that would like to see the important restrictions of the Clean Air Act substantially weakened.

[2] The 1978 Lead Standard. The Labor Department's Occupational Safety and Health Administration (headed by Thorne Auchter) wants to replace "maximum protection of workers" as the standard for pollution in lead industries with a "cost-benefit analysis" of individual safety measures. The proposed slackening of health controls could affect 835,000 American workers in at least 120 occupations.

[3] The 1971 Lead-Based Paint Poisoning Prevention Act. Run primarily by the Center for Disease Control, the program established under this act has already screened 3,475,659 children and referred 227,904—that's more than a quarter of a million!—youngsters to pediatric care for treatment of elevated blood-lead levels. This vital public health aid has been extended and expanded three times since its inception but is now slated to expire this November.

If you'd like to help create public pressure for the continued reduction of lead in the air and the workplace, or for the reestablishment of our only nationally effective lead-screening program for children, you may want to write your elected federal representatives and voice your concerns. (You can find out the names and addresses of these individuals by phoning your local public library.)

Lead poisoning is the number one neurological disease of children in this country. Yet even today, scientists admit (as Dr. Jane S. Lin-Fu pointed out in the January/February 1979 issue of Children Today) that it's "a uniquely neglected public health problem." Furthermore, lead poisoning is especially insidious because so often it slips by unidentified, damaging children's health and mental potential without anyone's even knowing the harm has occurred!

It's simply not enough to try, like an ostrich, to isolate yourself by hiding your head in the ground. After all, even that soil may not be safe anymore!

EDITOR'S NOTE: The National Center for Appropriate Technology has just published a booklet, compiled by the Boston Urban Gardeners, that outlines the dangers of lead poisoning and the steps you can take to garden more safely. 

In addition, the Center for Disease Control (Department of Health and Human Services, Public Health Service, Center for Disease Control offers two free handouts on lead: a reprint of Dr. Lin-Fu's "What Price Shall We Pay for Lead Poisoning in Children?" (which contains a history of the problem) and Preventing Lead Poisoning in Young Children (a technical booklet for physicians and health service personnel covering cause, identification, and treatment of plumbism).  

MOTHER would like to thank the Boston Urban Gardeners (particularly Charlotte Kahn and Julie Stone), Rufus L. Cha ney, Linda Roth, the Center for Disease Control, NCAT's Nancy Goodman, and especially Ben Barber—who alerted us to the seriousness of the lead poisoning issue—for their kind help in gathering much of the information for this article.  


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