CHAPTER 2

Setting the Stage: Historical Milestones in the Reduction of Lead in the Americas



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LEAD IN THE AMERICAS: A call for action CHAPTER 2 Setting the Stage: Historical Milestones in the Reduction of Lead in the Americas

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LEAD IN THE AMERICAS: A call for action SETTING THE STAGE: HISTORICAL MILESTONES IN THE REDUCTION OF LEAD IN THE AMERICAS ELLEN SILBERGELD*/CHRISTOPHER HOWSON** KIMBERLY BREWER** Lead poisoning is one of the most serious and prevalent diseases of environmental and occupational origin in the Americas. Yet, it is entirely preventable through the identification and control of exposures to lead. Lead poisoning is caused by acute or chronic exposures to lead through contamination of air, drinking water, foods, paint, soils, and dusts, as well as through the use of products that release lead such as leaded glazes on ceramicware and cans with lead solder. Lead poisoning is emblematic of the blurring of occupational and environmental health problems for three reasons: first, lead industries are often major sources of ambient environmental contamination; second, small-scale or cottage industries that use or handle lead increase the rate of exposure for workers and their families employed in these sectors; and third, workers in mining, industry, and construction can bring lead dusts home on their clothing or skin, thus exposing other family members to lead. Lead poisoning in the Americas, as elsewhere, is both a product of economic development and an indicator of economic and other disparities within societies. Too often, the poor and disadvantaged are at highest risk for lead poisoning because of employment in hazardous industries or residence near lead sources or in shelters containing paints with high levels of lead. Certain traditional practices of ceramic glazing and the use of lead-containing cosmetics and folk medicines also expose significant populations in our hemisphere to high levels of lead. Knowledge of the dangers associated with lead extends almost as far back as human discovery of the useful properties of this common element. In the Americas, lead became an important part of early economic development soon after the arrival of the Europeans. The Spanish, for example, began * University of Maryland Medical School, Baltimore, M.D. ** Institute of Medicine, Washington, D.C.

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LEAD IN THE AMERICAS: A call for action the extensive exploitation of the Zacatecas silver mines (which contained lead in the ores) in Mexico in the sixteenth century, and the Portuguese and Spanish brought lead-based glazes to the traditional ceramicists of the Americas. In North America, lead mines were quickly developed in the mid-Atlantic region, and lead-based paints were one of the first nonagricultural exports of the English colonies. As shown in Figure 2-1, these events in the American hemisphere contributed significantly to worldwide lead use and left their residues in environmental sinks as remote as Greenland (Hong et al., 1994). Indeed, the greatest impact of lead on human and environmental health was an American contribution: the invention and use of alkyllead (tetraethyl lead) as an antiknock additive to gasoline, which has resulted in the uncontrolled dispersion of millions of tons of lead throughout the world, most intensively in the cities and megacities of the Americas. Public health concerns over the growing lead exposures in the Americas also developed quickly. In the Massachusetts Bay Colony of colonial America, the addition of lead to wine and cider was banned in the early eighteenth century, and concerns over lead in drinking water and the printing process were expressed by Benjamin Franklin, Charles Dana, and others (Wedeen, 1984). In the mid-nineteenth century, reports were published in Mexico of severe lead intoxication among ceramicists and those consuming food prepared in lead-glazed pots (Ruíz-Sandoval, 1878). In 1914, the dangers of lead-based paint for children were reported in the U.S. city of Baltimore, Maryland (Fee, 1990). These and other findings spurred several countries of the Americas, including Argentina, Chile, Cuba, Colombia, Mexico, Nicaragua, Panama, Suriname, Uruguay, and Venezuela, to sign the International Labour Organization 's Agreement on Lead-Based Paint in the 1920s. The introduction of lead into gasoline in the 1920s was vigorously protested in the Americas by some leaders in occupational medicine. Nevertheless, effective actions to reduce lead use were not systematically undertaken in the hemisphere until the 1970s, largely because of the ability of the influential lead industry to control both scientific research and government policies in prior decades. Industry efforts and political indecision succeeded in preventing regulations on lead in gasoline, plumbing, paints, and canning for over 50 years, long after the hazards of these products and uses were known (EDF, 1992). It is now recognized, as summarized in the National Research Council report, Measuring Lead Exposures in Infants, Children, and Other Sensitive Populations (NRC, 1993), that lead is toxic to humans at very low levels (see Figure 3-2 in Chapter 3). As a basis for prevention, in 1991 the U.S. Centers

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LEAD IN THE AMERICAS: A call for action Figure 2-1. Greenland ice evidence of hemispheric lead pollution two millenia ago by Greek and Roman civilizations. Source: Reprinted, with permission, from Hong, S., J.P. Candelone, C.C. Patterson, and C.F. Boutron, “Greenland ice evidence of hemispheric lead pollution two millennia ago by Greek and Roman civilizations,” Science 265(5180):1841-1843. ©1994 by the American Association for the Advancement of Science. Note: Fig. 2-1. (A) Changes in worldwide lead production over the past 5,500 years. (B and C) Changes in lead concentration and lead crustal enrichment factor in central Greenland ice from 2,960 to 470 years ago. Each data point was obtained from the analysis of a core length corresponding to exactly two years of ice accumulation (except one, for which it was only 1 year because of poor core quality) to eliminate the influence of possible short-term (seasonal) changes in lead deposition.

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LEAD IN THE AMERICAS: A call for action for Disease Control and Prevention (CDC) defined a blood lead concentration in excess of 10 µg/dl as a cause for concern (CDC, 1991). CDC's finding was based on extensive epidemiologic studies and basic research that consistently demonstrated adverse health effects of lead—at and above these levels of exposure—on cardiovascular function in adults and neurobehavioral and cognitive attainment in children. Lead intake also damages the kidney and liver and adversely affects reproduction. Despite the progressive lowering of the threshold of safety over the past 25 years, a historical perspective on lead toxicity, as shown in Figure 2-2, suggests that the question of whether there is indeed a threshold, or “safe,” level of lead exposure is largely irrelevant in the context of global contamination, which has resulted in blood lead levels in even remote populations that are over 100 times those of our preindustrialized ancestors (Silbergeld, 1995). Figure 2-2. How Low is Toxic? Lead in perspective: blood lead levels in various populations and safety thresholds. Source: Silbergeld, E.K., “The international dimensions of lead exposure,” Intl J Occ and Envir Hlth 1:336-348, 1995. Reprinted with permission. Note: the LD50 for lead in children (100 µg/dl) is estimated from reports in the older clinical literature, although it is likely to be quite variable, depending upon the duration of exposure and the age of the child (Silbergeld, 1995). the CDC level of concern, 10 µg/dl, was set in 1991 (CDC, 1991). The median blood lead level for the U.S. population in 1990 was estimated to be 5 µg/dl (Brody et al., 1994). The lowest blood lead levels commonly found in many recent studies are about 1 µg/dl (NRC, 1993). Data on remote biota have been published by Rabinowitz, Flegal, and others (NRC, 1993). Blood lead level in preindustrial humans, 0.01 µg/dl, was estimated from measurements in bone (Silbergeld, 1995).

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LEAD IN THE AMERICAS: A call for action This relatively recent increase in internal dose makes it unlikely that humans, and other biota, have been able to adapt to an element with no known essential role in physiology. National actions to prevent lead exposures in most of the countries of the world have been slow in coming; as a result, lead production and use continue to expand. Recently, however, public health policy has been expanded to consider broader, internationally coordinated options for preventing lead poisoning. Broad global strategies have been identified in meetings of the Organization for Economic Cooperation and Development (OECD), United Nations Conference on Environment and Development (UNCED), and the Commission on Sustainable Development (CSD) (Silbergeld, 1995). It was recognized in many of these meetings that surveillance and data collection to assess the prevalence of lead poisoning internationally are critical to gain political momentum and recognition of lead as a public health problem. The Earth Summit Watch, formed in preparation for the United Nations Conference on Environment and Development in 1992, consists of a group of nongovernmental organizations interested in conducting country-by-country surveys of specific indicators of environmental problems. The Earth Summit Watch Survey Team, in 1993 and 1994, asked countries to indicate what they had done to address specific environmental issues, including lead exposure, and then made their survey results available in the report Four in ‘94 (NRDC and CAPE 21, 1994). The report is intended to help officially monitor govemment performance in programs designed and implemented to limit environmental degradation. Strategies directed toward lead exposure reduction within the region of the Americas have also been identified. In 1994, the U.S.-based nonprofit organization, the Alliance to End Childhood Lead Poisoning, hosted the first international conference to focus specifically on prevention of lead poisoning. The major goal of the conference, Global Dimensions of Lead Poisoning, was to increase international awareness of the causes and adverse effects of lead poisoning and to promote international collaboration in developing and implementing permanent, workable solutions and policies for prevention. Immediately following the conference, the United Nations Commission on Sustainable Development (CSD), established by the General Assembly in 1993, passed a resolution emphasizing the seriousness of lead poisoning as a public health problem. The end of 1994 saw the Summit of the Americas, which was convened in December in Miami, Florida, and attended by 34 heads of state from the

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LEAD IN THE AMERICAS: A call for action hemisphere. At the summit, all heads of state agreed to the phase-out of leaded gasoline in the hemisphere. In March 1995, the U.S. Environmental Protection Agency and the Mexican Ministry of Environment, Natural Resources, and Fisheries cohosted the International Workshop on Phasing Lead Out of Gasoline to discuss the feasibility and logistics of phasing out leaded gasoline in countries that had not yet done so. The workshop concluded with a request to the CSD that it formally adopt a resolutiori to phase out leaded gasoline. After a lengthy debate, the CSD honored this request in May 1995. It was against this backdrop of increasing regional activity that the U.S. Institute of Medicine and the National Institute of Public Health of Mexico conducted the conference summarized in this report. This activity was designed to build on the work of these previous efforts by: (1) focusing on the multiple major sources of lead exposures in the Americas and (2) convening a broad range of interested and affected parties to generate specific action steps to reduce lead toxicity across the region, and to do so in ways that may be broadly accepted and cost-effective.

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LEAD IN THE AMERICAS: A call for action CHAPTER 3 Plenary Sessions

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