Project at a Glance

Title: Particulate air pollution and morbidity in the California Central Valley: a high particulate pollution region.

Principal Investigator / Author(s): Van Den Eeden, Stephen.

Contractor: Kaiser Permanente, Northern California Region

Contract Number: 97-303

Research Program Area: Health & Exposure

Topic Areas: Health Effects of Air Pollution


The purpose of this study was to evaluate the relationship between particulate air pollution and morbidity among the Kaiser Permanente (KP) membership who reside in the Central Valley (CV) of California. Daily augmented particulate matter (PM) monitoring in the Central Valley was instituted as of November 1996 as part of a special monitoring program by the California Air Resources Board (CARB). The combination of the ambient air pollution data collected as part of the enhanced monitoring and the morbidity data from Kaiser Permanente provided an excellent opportunity to explore this relationship in an area with varied particulate matter.

We conducted time-series analyses examining the association between daily ambient measures of particulate matter (including PM chemical components), other criteria air pollutants (e.g., ozone, NO2, and CO), and daily admissions to the emergency room or hospitalization for respiratory and cardiovascular conditions among members of Kaiser Permanente, Northern California Region (KPNC) living in the Central Valley of California. Only those KPNC members who resided in an area where exposure could be assigned using one or more of the PM monitoring stations were included in the study. The study period was from January 1996 to December 2000.

Exposure was assigned based on each KP member's residential zip code and linked to the city where a monitoring station was in place. Morbidity data were derived from computerized data sources at Kaiser Permanente. Each health event of interest was identified and the age, gender and diagnosis ascertained. Outcome events were classisfied into one of three categories; cardiovascular, acute and chronic respiratory conditions, and two types of admissions; hospitalizations and emergency room visits. Preliminary analyses of the data included graphical techniques and bivariate analyses. Non-parametric smooths were developed that first fit confounding variables to each set of outcome data. These factors included long-wave terms (time), day-of-week, temperature, and humidity. In addition, because there were four population centers in this study a set of indicator variables for center was also included. Following the derivation of these first models, individual pollutants were then entered in the model.

Consistent adverse health effects were observed between a variety of air pollution metrics and acute and chronic respiratory hospitalizations and emergency room visits among Kaiser Permanente members living in the Central Valley of California. These associations were consistent across type of analysis and type of admission (hospitalization or emergency room visit). Of the pollutants studied PM10 and PM2.5 were consistently associated with increases in hospitalizations and emergency room visits for acute and chronic respiratory conditions. To a lesser extent CO and NO2 were associated with increases in admissions for all outcomers in our study. In contrast to the PM10 and PM2.5 results, we did not find convincing evidence of an association between the coarse fraction of PM and our outcomes. In addition, our results for cardiovascular admissions were inconsistently or not at all associated with the pollutants were studied. Finally, some of our pollutant-outcome associations were in the opposite direction from what we expected, most notably ozone.

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