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Lead in Mexican Craftworks
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Liliana Castillo
December 11, 2008
Introduction
For more than five centuries, the lead glaze technology brought to the Americas by
the Spanish has been essential to the creation of a unique Mexican craftworks tradition.
Today, lead glazed pottery is one of the greatest sources of lead exposure for Mexicans,
especially children. Although the leaching of lead from certain glazes has been
acknowledged for centuries, it is not until recent decades that the public has seen attempts to
regulate or solve the problem. Occasional exposure to lead has been documented among a
number of different occupations but the level of poisoning discovered in those in the ceramics
and pottery industry of Mexico has been, proved through various studies, high enough to
produce detrimental health effects and raise environmental concerns. This often means little
though, to nearly 500,000 Mexican potters and their families whose subsistence depends on
making these traditional leaded glaze ceramics and who do not see the hazards of lead right
away. It is thus a continuing struggle for the Mexican government to rid craftworks of lead.
Lead in Ceramics/Pottery
The artisans creating Mexico’s traditional ceramic craftworks are usually habitants
of a small pueblo or settlement with less than 2,500 people. They support their families
mainly by the making and selling of traditional clay crafts and dishes that are decorated
with a leaded glaze. Pottery is first painted, then finished and glazed with lead oxides such
as greta, a mixture of approximately 80% lead oxide and 20% water, to produce the
desired glazed result. To give the greta better adherence, the fired pots are cleaned by
rubbing away the ash marks and surface irregularities with a fabric. This process is usually
done by the potter’s assistant which might include children.
Before the second firing of the pots, the glaze is quickly applied by bathing the
whole or part of the pot in a tin containing the mixture of lead monoxide and water. It is
then set to dry. Sometimes, to get a black glaze, a potter might mix a black powder with
the lead monoxide and water and it is then applied with a brush. The leaded glaze,
besides serving aesthetic purposes, is used to help prevent the food from sticking to the
inside of cooking utensils. Then the glaze is also applied to the outside so that the pot
yields better resistance in the fire for cooking. When in contact with acidic foods however,
such as tomatoes and chili, both a staple of any Mexican diet, the lead in the glaze is
leached onto the foods and therefore enters the blood through the digestive system.
Exposure to lead is also obtained through the respiratory system. During the firing
process of lead-glazed ceramics, significant amounts of lead are released into the air.
Several results of various studies have shown that lead absorption may be increased in
children who live in communities where kilns, such as the one picture below, release lead
into the air. Air may be the most significant source of lead for them.
Children Exposed to Lead
Health Issues
Young children in Mexico are especially at risk of lead poisoning for various reasons. They
are first of all, highly exposed to it simply by living in a ceramics producing town. Lead-glazed
pots fired in simple kilns release lead into the atmosphere. Also, the children might play in
contaminated soil or be directly exposed, through their families, to the ovens and the greta. It is
of great concern to watch high lead blood levels in children because it affects them differently
than it does to adults. The potential for adverse effects is heightened in children because the
intake of lead per unit of body weight is higher and their bodies are still rapidly developing. Lead
is also very chemically similar to calcium and is rapidly absorbed by young children’s bodies.
Children can also be affected through their mother’s blood lead content while still in the womb.
Several birth defects have been correlated with a high blood lead level.
The adverse effects of lead in the human
system have been documented for
centuries. They include mild symptoms of
nausea, abdominal pain, excessive
lethargy or hyperactivity, and chest pains.
More extreme long-term symptoms
include seizures, comas, and death.
Studies
The World Health Organization indicates that the pre-industrial or natural blood lead level
in humans is estimated to have been about 0.016 mg/dl. A concentration of over 15 μg/dL
is considered a high blood level.
Oaxaca, Mexico:
(Rural area) Sample of 553 men and women over the age of 15 years; data was collected
for 413 subjects. The mean blood lead concentration of the entire study group was 43.8
mg/dl, the median at 43.2 mg/dl, with concentrations ranging from 8.4 to 99.6 mg/dl. Men
tended to have higher concentrations than women. Among nonpotters, people using leadglazed cooking utensils tended to have higher concentrations of lead in their blood.
Around 30% of the Mexican urban population uses these utensils.
Mexico City, Mexico:
(Urban area) Sample of 527 women residing in Tlalpan, the southern district of Mexico
City; among them, 107 women provided blood samples. Blood lead levels ranged from 1
to 52 μg/dL, with a mean of 10.6 μg/dL. Five percent of the women had a blood lead level
over 25 μg/dL and 22 % over 15 μg/dL. Concluded that the risk of high blood lead content
attributable to use of lead glazed ceramics was 58%. “This emphasizes the public health
importance of investigating lead glazed pottery in Mexico City and highlights the benefit
expected by the regulation of the lead content in pottery production” (Environmental
Health Perspectives, 1991, p119).
Figure 4
http://www.aidtoartisans.org/site/DocServer/usaid_lea
dfree_frontline.pdf?docID=822
Figure 3: World Health Organization
Policies and Regulations
Mexico’s position as a major lead producing country has brought about strong measures to
minimize potential sources of lead exposure. Since 1991, the implementation of surveillance
systems has reduced air lead concentrations. More recently, the establishment of regulations
through the Health Industry on numerous products including lead-glazed ceramics. A lot of
these measures include public education on the issues:
“An important element of these programs is an informed population. Parents who know the
potential sources of lead exposure can and likely will act to decrease exposure by regularly
washing younger children's hands, teaching older children to wash their hands often, and
avoiding the use of lead-glazed ceramic ware to prepare or store food” (Environmental Health
Perspectives, 1995).
Blood Lead Concentrations in Ceramic Folk Art Workers
Conclusion and Future Directions
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The folk art of Mexican pottery and ceramics making has deep traditional roots that slows
any change in the production of it. The growing concern for lead poisoning from lead-based glazes
has caused the Mexican government to look for solutions. Working with international agencies
such as UNESCO, the Lead-Free Pottery Alliance, USAID, Aid to Artisans, and the Mexican
Foundation for the Development of Folk Art, Mexican chemists have now created lead-free glazes
that work as well as the traditional lead-based formulas. This advance will not only improve the
health of the local population but it will open an international market of the products of these
artisans, previously unable to meet export market standards of lead-free pottery. This will then
provide an economic incentive for artisans to make the switch to lead-free glazes. USAID mission
director Edward Kadunk Jr. explains, “We think that Aid to Artisans will create better economic
opportunities for Mexican potters by opening markets and developing products that can compete
in global markets”. It is certainly a progressive step to better the lives of many people.
References
Ceramic Production in San Marcos Acteopan, Puebla, Mexico. Druc, Isabelle C. Ancient Mesoamerica, 2000, Vol. 11, p77-89
Figure 2. High blood lead levels in ceramic folk art workers in Michoacan, Mexico. Fernandez, Gustavio Olaiz; Martinez, Rosalba Rojas.
Archives of Environmental Health, Jan/Feb97, Vol. 52 Issue 1, p54
Why the opposition to ban lead?
Figure 1. http://www.flickr.com/photos/citlali/398157371/
If lead has been known to be toxic for so many years, why has the government and the
people been so hesitant to ban it? There are several answers. First of all, the livelihoods of
about 1.5 million families depends on the production of leaded glazes. The production of their
craftworks is largely possible due to the inexpensive component of lead, to take this away is
to deprive these families of a means of making pottery economically. Secondly, substitutions
for lead are being experimented with but none of the new glazes produces the same shine or
tone as the leaded glaze. This is what produces traditional colors and in a culturally rich
country like Mexico, tradition is strong. Lastly, both potters and consumers do not see a
cause and effect relationship in terms of lead poisoning since it happens so slowly and
gradually often producing many symptoms that could have been caused by a variety of other
things.
Environmental Lead Exposure: a Public Health Problem of Global Dimensions.Tong, Shilu; von Schirnding, Yasmin E.; Prapamontol, Tippawan. Bulletin of the
World Health Organization, 2000, Vol. 78 Issue 9, p1068-1077
.
Environmental Urban Lead Exposure and Blood Lead Levels in Children of Mexico City Romieu, Isabelle; Carreon, Tania; Lopez, Lizbeth; Palazuelos,
Eduardo; Rios, Camilo; Manuel, Yves; Hernandez-Avila, Mauricio. Environmental Health Perspectives, 1995, Vol. 103 Issue 11
Factors Associated with Lead Exposure in Oaxaca, Mexico. Hernandez-Serrato, Isidra; Mendoza-Alvarado, Laura; Rojas-Martinez, Rosalba;
Gonzalez-Garza, Carlos; Hulme, Jennifer Megan; Olaiz-Fernandez Gustavo. Journal of Exopsure Analysis and Environmental Epidemiology, Sep2003, Vol. 13
Issue 5, p341-347
Getting the Lead Out in Mexico. Mindling, Eric. Ceramics Monthly, Mar2002, Vol. 50 Issue 3, p16
High blood lead levels in ceramic folk art workers in Michoacan, Mexico. Fernandez, Gustavio Olaiz; Martinez, Rosalba Rojas. Archives of
Environmental Health, Jan/Feb97, Vol. 52 Issue 1, p51-55
Lead Elimination by Traditional Acidic Curing. Torres-Sanchez, Luisa; Lopez-Carrillo, Lizbeth; Rios, Camilo. Salud Pública de México, 1999, Vol. 41 Issue 2,
pS105-S108
Lead-Free Mexican Pottery Sells Better (2003, October). Retrieved December 7, 2008, from
http://www.aidtoartisans.org/site/DocServer/usaid_leadfree_frontline.pdf?docID=822
Lead-Glazed Ceramics as Major Determinants of Blood Lead Levels in Mexican Women. Hernandez Avila, Mauricio; Romieu, Isabelle; Rios, Camilo; Rivero,
Aracely; Palazuelos, Eduardo. Environmental Health Perspectives, 1991, Vol. 24 p117-120
Lead in Mexican Children. Weinhold, Bob. Environmental Health Perspectives, Jul2004, Vol. 112 Issue 10, pA569-A569
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