Mycotoxin reduction in Bt corn: potential economic, health, and regulatory
Environmental, Occupational Health, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto St.,
Pittsburgh, PA, 15261, USA
Received 1 July 2005; accepted 16 November 2005
Key words: Bt corn, economic impacts, health impacts, mycotoxin reduction, regulatory policy
Genetically modified (GM) Bt corn, through the pest protection that it confers, has lower levels of
mycotoxins: toxic and carcinogenic chemicals produced as secondary metabolites of fungi that colonize
crops. In some cases, the reduction of mycotoxins afforded by Bt corn is significant enough to have an
economic impact, both in terms of domestic markets and international trade. In less developed countries
where certain mycotoxins are significant contaminants of food, Bt corn adoption, by virtue of its mycotoxin
reduction, may even improve human and animal health. This paper describes an integrated assessment
model that analyzes the economic and health impacts of two mycotoxins in corn: fumonisin and aflatoxin.
It was found that excessively strict standards of these two mycotoxins could result in global trade losses in
the hundreds of millions $US annually, with the US, China, and Argentina suffering the greatest losses. The
paper then discusses the evidence for Bt corn’s lower levels of contamination of fumonisin and aflatoxin,
and estimates economic impacts in the United States. A total benefit of Bt corn’s reduction of fumonisin
and aflatoxin in the US was estimated at $23 million annually. Finally, the paper examines the potential
policy impacts of Bt corn’s mycotoxin reduction, on nations that are making a decision on whether to allow
commercialization of this genetically modified crop.
Transgenic Bt corn contains a gene from the soil
bacterium Bacillus thuringiensis, which encodes for
formation of a crystal (Cry) protein that is toxic to
common lepidopteran corn pests. It is one of the
most commonly grown transgenic crops in the
world today. In 2004, Bt corn was grown on about
27% of field corn acres in the United States
(USDA, 2004). Seven nations other than the
United States are planting Bt corn currently.
These are: Canada, Germany, Spain, Argentina,
Honduras, South Africa, and the Philippines
(James, 2003). The US is by far the largest
adopter, with 85% of the total global acreage of
Bt corn. Argentina, Canada, and South Africa are
also important adopters; comprising 8, 4, and 2%
respectively of the total global Bt corn acreage.
China has approved field trials, but has not yet
allowed commercialization of the crop. The other
Bt corn-adopting nations comprise only 1% of
the world market. In total, about 25 million acres
of Bt corn are planted globally today (James,
Through Bt corn’s reduction of pest damage,
one indirect benefit that has emerged from Bt
corn adoption is lower levels of mycotoxin con-
tamination. Mycotoxins are secondary metabo-
lites of fungi that colonize crops. They are
considered unavoidable contaminants in foods,
Transgenic Research (2006) 15:277–289
? Springer 2006
as best-available technologies cannot completely
eliminate their presence in crops (CAST, 2003).
Insect damage is one factor that predisposes corn
to mycotoxin contamination, because insect her-
bivory creates kernel wounds that encourage
fungal colonization, and insects themselves serve
as vectors of fungal spores (Sinha, 1994; Wicklow,
1994; Munkvold & Hellmich, 1999). Thus, any
method that reduces insect damage in corn also
reduces risk of fungal contamination. Indeed, in a
variety of field studies, Bt corn has been shown to
have significantly lower levels of common myco-
toxins (Benedict et al., 1998; Munkvold & Hell-
mich, 1999; Dowd, 2001; Bakan et al., 2002;
Williams et al., 2002; Hammond et al., 2003).
Mycotoxins are an important regulatory con-
cern worldwide today because of their toxic and
carcinogenic effects in humans and animals. Bt
corn and other transgenic crops are yet another
hotspot of global regulation. Yet the benefit of Bt
corn’s reduction of mycotoxin damage has been
virtually ignored in policy debates anywhere in the
world. As adoption of agricultural biotechnology
continues to increase on a global scale, policy
makers worldwide should consider the economic
and health impacts of this secondary benefit of
transgenic pest-protected crops. Mycotoxin reduc-
tion has already had significant economic impacts
in the United States at current levels of Bt crop
planting (Wu et al., 2004). In less developed
countries (LDCs), the mycotoxin reduction that
Bt crops can provide could have important eco-
nomic as well as health impacts. Thus, it is an
important aspect to consider when developing
regulatory policies on Bt crops.
Mycotoxins in corn: fumonisin and aflatoxin
mycotoxins are fumonisins and aflatoxins. Fumon-
isins are found almost exclusively in corn; while
aflatoxins are found in a variety of crops including
corn, cotton, peanuts, pistachios, almonds, and
walnuts (Robens & Cardwell, 2003). Fumonisins
are produced by the fungi Fusarium verticillioides
(formerly F. moniliforme) and Fusarium proliferatum
(IARC, 2002). They were first discovered in 1988 in
connection with two events in two different parts
of the world: high human esophageal cancer rates
in Transkei, South Africa; and unusually high
of the most agriculturallyimportant
horse and swine death rates in the United States
(Marasas, 1996). Now more than 28 types of
fumonisins have been isolated and characterized
worldwide, of which fumonisin B1 (FB1) is the
most common in corn (Rheeder et al., 2002).
Consumption of fumonisin has been associated
with elevated human esophageal cancer incidence
in various parts of Africa, Central America,
and Asia (Marasas et al., 2004) and among the
black population in Charleston, South Carolina
(Sydenham et al., 1991). Because FB1 reduces
uptake of folate in different cell lines, fumonisin
consumption has been implicated in connection
withneural tube defects
(Hendricks, 1999; Marasas et al., 2004). No con-
firmed cases of acute fumonisin toxicity in humans
have been found. Fumonisins can be highly toxic
to animals, causing diseases such as equine leuko-
encephalomalacia (ELEM) in horses and porcine
pulmonary edema (PPE) in swine (Ross et al.,
Aspergillus flavus and Aspergillus parasiticus, and
are the most potent chemical liver carcinogens
hemorrhage, acute liver damage, edema, and
possibly death, can result from extremely high
doses of aflatoxin. More common are health
effects associated with chronic low to moderate
levels of aflatoxin consumption. For people who
are infected with hepatitis B and C (common in
China and sub-Saharan Africa), aflatoxin con-
sumption raises more than tenfold the risk of liver
cancer compared with either exposure alone
(Miller & Marasas, 2002). Aflatoxin consumption
is also associated with stunting in children (Gong
et al.,2000) andimmune
(Turner et al., 2003). Aflatoxins cause a variety
of illnesses in animals as well. In poultry,
aflatoxin consumption results in liver damage,
impaired productivity and reproductive efficiency,
decreased egg production in hens, inferior egg-
increased susceptibility to disease (Wyatt, 1991).
In cattle, the primary symptoms are reduced
weight gain, liver and kidney damage, and
reduced milk production (Keyl, 1978). Unfortu-
nately, loss of income from decreased animal
production can leads to greater poverty among
farmers, reinforcing conditions conducive to poor
human health (Miller & Marasas, 2002).
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