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In December, 1994, a 42-year-old former El Paso, Texas, resident with multiple sclerosis (MS) contacted TDH to report an apparent cluster of MS cases among people who spent their childhood in the Kern Place-Mission Hills area of El Paso. Based on initial referrals, 15 adults (ages 42 to 53) with MS who resided in the neighborhood as children were identified by TDH. Fourteen of the 15 people attended the Mesita Elementary School, a neighborhood public school. One person had attended a private school.
Twelve of the former Mesita Elementary School students reported a diagnosis of definite MS by a neurologist; two reported a diagnosis of probable MS. Applying a national prevalence rate estimate of 102/100,000 to the estimated 3,100 students who attended the Mesita school from 1948 to 1970, approximately three cases of MS would have been expected. During the 1950s and 1960s, the population of the Kern Place-Mission Hills area of El Paso was predominantly non-Hispanic white.
Early in the investigation, concerns were raised by former Mesita students about the possible impact of a local metals smelter, particularly past operations at the facility. Mesita Elementary School is located approximately one mile east-northeast of the smelter. Historically, high levels of metals have been documented from the facility's air emissions.
The closest elementary school and residences to the smelter during the 1950s and 1960s were in Smeltertown, located on the smelter's property immediately adjacent to the smelter facility. In contrast to the Kern Place-Mission Hills neighborhood, the majority of Smeltertown residents were Hispanic and the neighborhood was considered one of the less affluent areas of El Paso. Due to extremely high levels of heavy metal contamination, Smeltertown's only elementary school, E.B. Jones Elementary School, was closed in the early 1970s. In addition, the entire community was evacuated and all the homes and buildings were razed at that time. No cases of MS were initially reported from former E.B. Jones students.
Based on the potential cluster of MS cases in the Mesita cohort and related environmental concerns, TDH submitted a grant to the Agency for Toxic Substances and Disease Registry (ATSDR) to examine the prevalence of MS in the cohort of former Mesita Elementary School students and to determine if the prevalence was elevated compared to national rates. We also proposed including former E.B. Jones students in the study, if information was available to enumerate the cohort. Funding for the investigation was received in late 1997. Data collection and analyses were completed in January 2001.