UT School of Public Health Reports Possible Link Between Ship Channel Air Pollutants, Cancer Risks
HOUSTON – (Jan. 19, 2007) – A new epidemiological study by researchers from The University of Texas School of Public Health at Houston reports for the first time a possible link between proximity to the Houston Ship Channel and increased risk of childhood cancer. The 18-month study was conducted at the request of the City of Houston in conjunction with ongoing efforts to reduce air quality health risks in Harris County.
The study explored possible connections between the incidence of lymphohematopoietic cancer and proximity to the Houston Ship Channel. Researchers also looked into potential links between these cancers and ambient levels of two hazardous air pollutants (HAPs): benzene and 1,3-butadiene.
UT School of Public Health Dean Guy S. Parcel, Ph.D., at the
podium during the City Hall news conference on the study of HAPs
and cancer in the Ship Channel area, Jan. 18. Behind him (left-right)
are: Ann L. Coker, Ph.D., doctoral student Kristina Walker and Houston
Mayor Bill White. (PHOTO by Rob Cahill)
Preliminary findings indicate that living nearer the Ship Channel and in census tracts with higher estimated 1,3-butadiene levels may be associated with childhood leukemia. Children living within two miles of the Ship Channel, according to the study, had a 56 percent higher risk for childhood leukemia than those living more than 10 miles away.
Principal investigator Ann L. Coker, Ph.D., a professor in the school’s Division of Epidemiology and Disease Control, cautioned that the preliminary study found an “association,” but was not detailed enough to prove that the air pollutants actually caused the illnesses.
Relatively rare, the incidence of childhood leukemia in Texas is four cases per 100,000 children per year, the Texas Cancer Registry reports.
“The science supports our claim that reducing these hazardous air pollutants must be a high priority for Houston,” said Houston Mayor Bill White at a Jan. 18 news conference to announce the final report. “The city has hired environmental experts and legal counsel and has aggressively negotiated with local industry, resulting in a reduction in 1,3 butadiene.”
Initial results indicate that higher benzene levels were not associated with leukemia or lymphoma in children. Among adults, neither proximity to the Ship Channel, nor estimated ambient levels of benzene or 1,3-butadiene, were consistently associated with leukemia or lymphoma.
“As a lifelong resident of the Ship Channel area and the representative of District I, I take this very seriously,” said Council Member Carol Alvarado. “I am encouraged by the progress we are making to cut these harmful emissions and protect our citizens, but we have a lot more work to do.”
Benzene and 1,3-butadiene were identified last June as major air quality health risks by a task force of experts assembled by The University of Texas Health Science Center at Houston to study air pollution. Among other sources, benzene and 1,3-butadiene are produced by petrochemical and synthetic rubber and plastics manufacturers. According to the International Agency for Research on Cancer (IARC), benzene is classified as a known human carcinogen and 1,3-butadiene is classified as a probable human carcinogen.
“Observing a specific health effect of HAPs in light of recently documented elevated levels of benzene and 1,3 butadiene in Houston strongly suggests a need to explore this issue further,” Coker said.
Investigators from the UT School of Public Health included Coker, Elaine Symanski, Ph.D., an associate professor in the Division of Environmental and Occupational Health Sciences, and doctoral students Kristina M. Walker and Philip J. Lupo.
“Research in the area of environmental health is an important part of our mission at the UT School of Public Health. We are committed to working with local and state government to provide information that may be helpful in establishing public health policy,” said Guy S. Parcel, Ph.D., dean of the UT School of Public Health.
“While recent reports have commented on the elevated ambient levels of hazardous air pollutants in certain areas of Houston, few studies have assessed the health effects of HAPs for Houstonians and none have evaluated the association between ambient levels of these pollutants and lymphohematopoietic cancer risk in this population,” said Walker, who conducted the analyses.
Leukemia, lymphoma and myeloma were selected for this investigation because they have been linked to benzene and 1,3-butadiene exposures in occupational epidemiological studies, Symanski said. The period of time required for the development of lymphohematopoietic cancers is short, compared to other cancers, she added.
Investigators determined the incidence of leukemias and lymphomas for all census tracts in Harris County using data provided by the Texas Cancer Registry (TCR) for the period of 1995 to 2003. Investigators then correlated census tract level incidence with estimated ambient levels of benzene and 1,3-butadiene using monitoring data collected by the Texas Commission on Environmental Quality (TCEQ) for 1992 to 2003. Researchers also measured the risk of childhood and adult leukemias and lymphomas related to proximity to the Ship Channel, Coker said.
Funding for the study came from Houston’s health department and the U.S. Centers for Disease Control and Prevention.
The study is available online at http://www.houstontx.gov/health/UT-main.html.