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Publication Number: FHWA-RD-98-182
Lead Abatement On Bridges And Steel Structures
Table of Contents
HISTORY OF LEAD AND ITS USES
After completing Section 1, you will be able to:
Before there was alar, dioxin, or radon to terrify people that an unseen menace was poisoning them, there was LEAD.
A malleable, durable metal, as old as civilization, as old as the lead-lined aqueducts that brought water to ancient Rome, as old as a medieval lead goblet hoisted to a friend's good health, lead has from the beginning had twin reputations as a valuable resource and deadly poison. Even in Hippocrates' time, Greek shipbuilders knew that long days of pouring lead into molds for keels would leave workers retching and delirious. Overtime meant death.
In the late 1700s, Ben Franklin described various environmental and occupational effects which he attributed to lead, affecting trades, such as printers, plumbers, and painters. These descriptions are found in a letter that Franklin wrote to a friend.
In the early 1900s, detailed information on the hazards began to appear. First, a study in Britain linked exposures to lead with high rates of infertility, stillbirths, and first year infant deaths. About the same time, an Australian study observed lead poisoning among children and identified household dust and paint as the sources of the lead. Childhood activities, such as nail-biting, thumb-sucking, and eating with fingers contaminated with lead are the ways lead was introduced into the body.
In this way, lead differs from many of the more recently minted environmental toxins; no need to wonder whether a substance that seems subtly dangerous in test tube experiments or animal studies might also pose a threat to humans. The evidence has been blatant for centuries. Eat a little lead often enough and you get sick; eat a little more and you can die.
But the idea that the metal might damage the mind long after other physical symptoms have abated, or even before they develop, has been slower to catch on. It was Herbert Needleman's mentor, a courtly Boston doctor named Randolph Byers, who provided some of the first clues.
As a Harvard professor and pediatrician at the Children's Hospital lead clinic in 1939, Byers treated inner city toddlers who had cut their teeth on the rails of lead-painted cribs or on window sills. Over the course of weeks or months, they developed the pallor, vomiting, and listlessness linked to overt lead poisoning. In those days doctors believed that if they could prevent the brain from swelling, there was no risk of long-term damage. After a few weeks of extra milk and cod liver oil, children treated for poisoning were sent home from the hospital "good as new."
On the hunch that damage from lead ran deeper than anyone imagined, Byers and Harvard psychologist Elizabeth Lord kept tabs on the children's mental development for several years. What they discovered worried them: By 1943, all but two of the 20 children in the study were having serious academic problems; several had not learned to read or write even by age eight or nine.
Tests also showed the sort of outbursts characteristic of people who suffered damage to the brain's cerebral cortex, Byers and Lord reported: "Three were excluded from school on the basis of behavior, one for setting fires in the school, another for repeatedly getting up and dancing on desks and other furniture and the third for sticking a fork into another child's face." Roman peasants often called their leaders mad when the rich used lead as a sweetener for food and drink.
To Lord and Byers, the most frightening aspect of their study was that this profound damage had such a quiet beginning. It seemed likely that many more toddlers than anyone imagined were having their intellects and, perhaps, personalities silently mangled right under well-meaning parents' noses.
The findings made an immediate splash in the press and public circles. A 1943 Times magazine article entitled "Paint Eaters" detailed the Byers-Lord study and warned: "If your child is slow with building blocks, but quick on tantrums, he may be a lead eater.... And not many Doctors realized that one consequence of the plumbic passion in children may be stupidity."
Previously we have discussed the use of lead in ancient times and the health effects that lead may have caused. Now lets speak about the use of lead in today's world.
MODERN DAY USES OF LEAD
Lead has been used since ancient times as a paint pigment. Two major chemical forms of lead are used as colors--they are called "white lead" (a lead carbonate) and "red lead" (a lead oxide). Both types of lead provide a thick, heavy, tough coating, one that does not crack through wear or temperature variations, because it can expand and contract in unison with the base metal to which it is attached. In addition, the chemical nature of lead causes it to provide corrosion resistance as well. Because of these properties, lead paints have been and continue to be widely used for bridges and other metal structures.
The overall amount of lead that has been used can be considerable--one estimate for the Sydney Harbor Bridge in Australia is that 90 tons of red lead paint and 250 tons of battleship gray are used in a five-year painting cycle. The bridge itself contains 51,300 tons of steel. Some old structures may have a thick coating from decades of painting. Even new steel is often coated with lead paint. This may be surprising to some, because many people are under the impression that lead paint has been banned. It is true that lead has been prohibited for use as a residential interior finish. But it continues to be used for many exterior uses. Even if lead were banned today for new use on structural steel, construction workers would still face a lead hazard for the next 25-50 years, because there are so many old structures that contain it. It is estimated that 35%-40% of steel structures are coated with lead-based paint, including 90,000 bridges. Of all bridges repainted in 1985-1989, 80% of them had lead coatings. Because demolition and repair are likely to be increasingly important in the future as the Nation faces its "infrastructure problems," it is important that every construction worker be aware of this hazard.
For some Laborers, the idea that the job can involve lead exposures may be a new one. After all, lead is not a common item on the work site. It is not often present in structural steel alloys, nor used as a specialty product. It may be present as a thin film of paint, but this may seem like an unlikely possibility for causing a problem. Well, if you ask anyone who has done any renovation or demolition work on old steel structures lately, you begin to understand the problem. It is typical to use oxyacetylene torches to cut on old steel structures or to use welding equipment to weld on them. The high temperatures of the torch or welding process vaporizes the lead, so it becomes airborne and available for the worker to breathe. The purpose of this course is to explain the nature of the hazard, provide recommended work practices to allow safe work, and to describe the relevant regulations and guidelines for lead. Because lead is such an important hazard, it is covered by a very tough OSHA standard. The Lead Standard will be reviewed in this course because it addresses many of the hazards involved with lead exposure.
Environmental Exposures to Lead
Environmental lead exposures are those that occur outside the workplace. Airborne lead, resulting from either auto emissions or industrial sources, represents an important source of this exposure. Direct breathing of lead dust in the air can contribute to lead intoxication, as can the intake of soil or dust which has been contaminated by lead. The elimination of leaded gasoline has contributed to the overall reduction of the environment lead levels. This effort has reduced levels of lead in the blood of the general population more than any other single factor.
Lead-contaminated drinking water also contributes to the level of exposure. In most cases, lead in water has been leached from lead tanks and pipes, or from lead soldered copper pipes by soft water with an acidic pH. pH is a measure of the acidic or basic nature of a liquid. Normally, water has a pH that is neutral or 7. By comparison, vinegar (acidic) has a pH of about 3 and drain cleaners (basic) have a pH of about 12.
Recreational use of lead can also be linked to similar problems found on steel structures. Both fishermen and waterfowl hunters that produce their own lead weights by heating bar lead to its molten state produce the same fumes which are given off by heating lead paint on bridges. Many outdoorsmen who produce their own lead weights, which they acquire from gas stations, also must contend with the problem of the petroleum byproducts found on the surface of the lead which are also heated and produce toxic fumes. Skin divers may also pour their own weight belts. Manufacturers are still producing lead shotgun shells for use on upland game. The problem here is not so much to the human but to the environment itself. Many game animals may only be wounded only to die later unfound by the hunter. Along comes a bird of prey, such as the eagle, and by eating the dead carcass the eagle can die of lead poisoning. This problem resulted in the use of steel shot for waterfowlers.
Lead is also used for stain glass window production. Here again the lead is made molten and then poured between the pieces of stained glass. This holds the glass in place and gives the window, lamp shade, or decoration a very distinct look. With this beauty also comes the health hazards associated with molten lead.
One other area in which lead may be found in the home is a crystal decanter. If alcohol is left in the decanter for any length of time the lead may leach into the alcoholic beverage causing the unsuspecting person to become ill.
Occupational Exposures to Lead
Occupational lead exposures are exposures that occur on the job. Adults working in lead-associated industries, such as smelting, auto body repair, battery manufacturing, and home remodeling, will have increased exposures to lead. In addition, they may expose their families by bringing lead-contaminated dust into their home with dirty work clothes, shoes, hair, and body.
It is the occupational exposures that are of concern to us in the removal or abatement of lead. There are many applications of lead and lead products that will create exposure as we do our jobs on construction, renovation and repair, or demolition.
In today's world anything which is made of iron/steel and comes in contact with the elements will develop a rust problem. Bridges, water towers, outdoor stadiums, and some electrical towers fall into this category. In order to have the iron/steel last it must have a protective coating placed upon it to preserve it. Paints with lead additives are the best way to protect the metals. Year after year the bridges of this country are coated over and over with lead paint.
Lead paint on bridges and structural steel and concrete creates hazards when cut with torches and saws. Lead melts at 621ºF and boils at 3164ºF, or well below the temperature at the tip of a cutting torch. The lead is vaporized when exposed to the high temperature of the torch and this vapor is then available to be breathed in. Dust is generated by cutting with cut-off saws, scraping or sanding, or sandblasting lead coated materials. This dust is also hazardous because it may be in the air (to be breathed in), or as larger dust particles. These particles settle on surfaces and hands, and can then be ingested when workers eat lunch or smoke.
Paint containing lead is used to protect the infrastructure from rusting out. Here the paint is applied to the steel member before being placed and acts as a protective barrier against air pollutants, acid rains, and anything else that may attack the metal and start its decay. Lead handles this job in a very effective way because of its elasticity, meaning it has the ability to move with the steel either in expansion or contraction.
During the construction of buildings, lead has been used in water and sewer pipes; joint materials for pipe; solder and electrical connections; linings of tanks, vessels, and vats; and roofing materials, such as cornices, gutters, and flashing. It is safe to say that when renovation or demolition occurs where lead-containing products are involved, there will be the potential for lead exposure.
Elsewhere in this manual you will learn of the effects on both the environment and on humans from lead-coated surfaces. Many laws are changing to protect the environment and the populations of this country. It is up to each and every one of you to make sure that the new laws are followed and you, your families, and the environment are protected.