Investigation of National and Regional Mortality and Morbidity Risks for the Air Health Indicator (AHI).

NOTICE OF PROPOSED PROCUREMENT (NPP)

Solicitation #: 1000173235 Closing Date: July 10, 2015 Time: 2 p.m. EDT

This requirement is for the department of Health Canada.

Title: Investigation of National and Regional Mortality and Morbidity Risks for the Air Health Indicator

Scope: Health Canada has recently developed a new methodology, the Air Health Indicator (AHI), for assessing the effects on daily mortality of short-term exposure air pollution for warm season from April to September, as they may vary dynamically over space and time in response to changes in air quality, and has been assessing its performance in simulation studies and applying it to 26 years (1984-2009) of data from 24 major Canadian Census Divisions (CDs). Hundreds of time-series studies of daily mortality have now been published worldwide, and are critical components of the scientific evidence supporting a causal relationship between air pollution and public health. The AHI provides time trends in annual risks at city-specific, regional and national levels such as an increasing, decreasing or constant trend over a time period of interest. The AHI can be used in policy analysis, with potentially important applications to the assessment of the public health impacts of air quality regulation.

For the AHI, health outcome (daily mortality) data from 24 Canadian cities was used and estimation of between city heterogeneity has been problematic due to the small number of cities involved. Applying least squares estimation (LSE), negative estimates that are meaningless have sometimes been obtained. To improve the estimation, a Bayesian MCMC approach has been employed to estimate the heterogeneity as well as national risks. In previous contracts we investigated the effects of prior distributions on parameters on the risk estimation and have found the use of non-informative prior distributions to be desirable. We have investigated region specific risk and variability for several different region definitions, which needs further exploration.

Estimation of short-term (or acute) risk due to air pollution is the main topic of the AHI and has been subject to much scrutiny in the recent contract. We have demonstrated a source of bias in current estimates of population health risk due to air pollution based on natural spline smoother of time and proposed a new smoother (Slepian smooth functions ) to reduce the compensates of this bias, resulting in estimates with more accurate interpretation.

In previous contracts we have developed a model for aggregating multiple lags of a pollutant together so as to provide a single estimate of risk. This estimate can be thought of philosophically as similar to a distributed lag effect, representing the acute risk due to the air pollutant across a number of lags. This approach called synthetic lag model offers a satisfactory and stable way of synthetically lagging pollutants to give estimates of risk which encapsulate multiple lags in one series.

So far the AHI has developed for mortality only on a single pollutant. It is desirable to consider multiple pollutants at a time as the population are always exposed to multiple pollutants. The main pollutants for the AHI are ozone and fine particulate matters