PARTICULATE MATTER AND SULFATE: EVALUATION OF CURRENT CALIFORNIA AIR QUALITY STANDARDS WITH RESPECT TO PROTECTION OF CHILDREN

Epidemiological evidence indicates that present-day ambient particulate matter (PM) and/or sulfate air pollution exposures are associated with adverse health effects in children, including that: Short-term PM and/or sulfate exposures to children are associated with: • reduced pulmonary function; • increased respiratory symptoms in asthmatics (e.g., asthma attacks) and non-asthmatics; • increased incidence of respiratory doctor’s visits; • increased incidence of emergency department (ED) visits and hospital admissions (HA’s); • increased mortality, and; • especially increased infant morbidity and mortality; Long-term chronic PM and/or sulfate exposures to children are associated with: • reduced lung function; • increased respiratory symptoms; and, • increased infant mortality, intrauterine growth reduction, or pre-term delivery. Especially apparent in the many studies examined, and of notable concern, are results indicating much higher risks for children in the neonatal (< 1 month) and post-neonatal (1-12 months) age groups. Furthermore, an examination of key medical visits and hospital admissions studies indicates that the existing Federal and California PM10 and PM2.5 mass and sulfate ambient air quality standards are not presently sufficiently protective of public health, as significant adverse health impacts have been documented in published studies at mean ambient levels below these standards. Both biological and physical exposure-related factors enhance the risk to children from PM and sulfate exposures. These risk-enhancing factors include: • higher PM concentration exposures resulting from children’s greater activity levels; • larger PM doses in children from increased ventilation rates; • greater doses of ultrafines among children 14-18 years of age; • enhanced PM doses in children, especially infants, per body weight and lung surface area; • diminished and developing defense systems in infants; • higher prevalence of children with asthma than in other age groups; • larger percentage of children made susceptible by poverty than other age groups; and, • gas-particle interactions and particle-allergen interactions, potentially making the individual pollutant standards not fully protective to susceptible populations, such as children. Based on the above insights, it is recommended that future PM research should focus on: • improved identification of the specific characteristics of PM (e.g., ultrafines, acidity, elemental composition, etc.) that are contributing most to noted PM effects, and quantification of their relative roles in PM toxicity; • further investigation as to whether acute exposures less than one day in length (e.g., 1-hr. daily maximum), or longer multi-day exposures (e.g., 2 or more day average PM), also have health importance, over and above that captured by the 24-hr. PM peak PM concentration measurement; i • further investigations into particle-gas and particle-allergen interactions; • using both experimental and epidemiological methods, conduct further investigations of apparently larger acute and long-term effects of PM on children, and especially infants.