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December 3, 2001
www.tdh.state.tx.us/phpej:TEA8 ST A'E Vol. 61 No. 25
UMFMTS CNfli I VIlW
El Paso Multiple Sclerosis Cluster Investigation
The primary purpose of the Environmental and Occupational Epidemiology Program (EOEP) of
the Texas Department of Health is to investigate and prevent diseases and adverse health condi-
tions related to environmental and occupational exposures. One way EOEP fulfills this purpose is to
investigate possible noncommunicable disease clusters. This report summarizes an investigation
the EOEP, in cooperation with the Agency for Toxic Substances and Disease Registry (ATSDR), con-
ducted in September 2001 to respond to the concerns of some El Paso residents that environmental
toxins could be responsible for a cluster of multiple sclerosis cases in their community.
In December 1994 a former El Paso
resident with multiple sclerosis (MS)
contacted TDH to report an apparent
"cluster" of MS cases among people who spent
their childhoods in the Kern Place-Mission
Hills area of El Paso. Early in the investigation,
concerns were raised about the possible impact
of air emissions from a local metals smelter,
particularly during the time prior to the
installation of pollution controls in the 1970s.
Established in 1887, the ASARCO smelter in
El Paso has processed primarily lead, copper,
cadmium, and zinc. ASARCO suspended
smelter operations in 1999. Historically,
ASARCO's air emissions have been documented
to contain high levels of metals such as iron,
lead, arsenic, zinc, and cadmium.
Through a cooperative agreement with
ATSDR in 1996, TDH examined the available
information about the MS cases and related
environmental concerns. TDH concluded
that the reported number of MS cases in the
neighborhood did appear to be high and
noted that previous studies in the scientific
literature had investigated the role of metals
exposure in the development of the disease.
It was not possible from the available infor-
mation for El Paso, however, to determine if
metals exposure was the cause of MS in this
area nor if there was a true excess of MS. The
report recommended a study be conducted
among persons who lived in the Kern Place-
Mission Hills neighborhood and in Smeltertown
during the 1940s, 1950s, and 1960s to deter-
mine the number of people who had been
diagnosed with MS. Smeltertown was a
community of residences owned by ASARCO
and located on the company's property. Each
neighborhood was served by one local public
elementary school, Mesita in the Kern Place-
Mission Hills area and E.B. Jones in Smeltertown.
TDH received a grant from ATSDR to examine
the prevalence of MS in the group of children
who lived in the two communities and at-
tended the two public elementary schools.
Because a list of children who lived in the
neighborhoods was not available, attendance
at the schools was used as a proxy for living
in the neighborhoods. The ATSDR grant also
allowed TDH to investigate what historic
environmental and biologic sampling data
might still be available for use if future studies
in the area were to be considered.
Study Overview
Students who attended Mesita or E.B. Jones
Elementary schools from 1948 through 1970
were eligible to be included in the study. The
former students were identified primarily
through school records. Questionnaires were
mailed to all former students for whom a
mailing address could be located. The ques-
tionnaire asked for demographic and medical
information. People who indicated they had
been diagnosed with MS were asked for copies
of their medical records. These medical records
were reviewed by a board-certified neurologist
to confirm the MS diagnosis.
From returned questionnaires, prevalence
estimates were calculated for the separate
cohorts of former students from Mesita and
E.B. Jones Elementary schools and for the
combined student cohort of both schools. The
actual number of MS cases found among the
former students was also compared with the
expected number based on national estimates
of MS prevalence. The comparison of the
actual or observed number of MS cases to the
expected number was done using a statistical
procedure known as a standardized morbidity
ratio (SMR).
Continued
Also in this issue
Bimonthly Statistical Summary
Vaccine Preventable Disease Update
Texas Department of Health
U of NT Dep. Libraries
76203
02-432
RECD MAY 22 2002