Research Program Area: Health & Exposure
Topic Areas: Health Effects of Air Pollution
In this final report on the pilot study phase, documentation is presented on all aspects of the two-year program. Because of the nature of this effort and its stage of completion, it is felt that the appropriate conclusions and recommendations relate to the effectiveness of the study protocol, rather than the tabulation of preliminary data analyses of questionnaire responses. The latter, however, are useful for two overall purposes -- to evaluate the current questionnaire and formulate necessary modifications and to assist in defining future study protocol and emphasis based upon findings. Analysis of reproductive outcomes (Section 4.2.8) reveals a key area requiring comprehensive treatment by means of questionnaire changes, expert consultation and use of a control group. Also based upon the pilot study findings (Section 4.2.9), it is recommended that a mortality component be incorporated into the study. In the pilot study, we have experienced a near negligible refusal rate ( < 5%) among those contacted. Furthermore, utilizing primary tracing methods approximately 75% of the total cohort have been located or have had their addresses updated. In order to effectively utilize the questionnaire data it is necessary to establish a control group. Two candidate control groups have been identified and contact was made in order to evaluate their record keeping and explore the willingness of their school districts to cooperate Conclusions about VCM exposure have been made on the basis of ambient measurement data and computer modeling. Since no direct measurements were taken at the school location until fairly recently, it is only possible to determine a likely range of concentrations based upon source estimates and meteorological dispersion relationships. It was found that although meteorological conditions varied sufficiently from year to year to affect exposure, there was too much uncertainty in other factors (especially in the emission rate) to justify differentiating student exposure on a year-by-year basis. Students in the cohort were therefore grouped according to the duration of their attendance. Annual average VCM concentrations at the school site were determined by modeling VCM emissions and dispersion during the school day (8 a.m. to 3 p.m.), from September through May. The Texas Episodic Model (TEM), a short-term Gaussian plume computer model, was used in conjunction with historical local meteorological data and a range of emission rate estimates.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
Stay involved, sign up with CARB's Research Email Distribution List