Lecture 5: Health Impact Assessment

what is HIA

A systematic approach used to estimate and evaluate the potential health effects—both positive and negative—of changes in air quality on a population. This can involve assessing the impact of a new project, policy, or program, or evaluating the effects of current air pollution levels.

characteristics of HIA

• evidence-based

• population wide assessment

• policy applications

• comprehensive

what is a population-wide assessment

assess the number of excess cases of a disease or death that may accur across a large population due to air pollution exposure

Identifying key hazards- Evaluation matrix

four components of HIA

1. air pollution

2. population

3. baseline health

4. health risk

all four equate to overall health impact

air pollution (question, sources, considerations, focus)

• how much air pollution is the popualtion exposed to?

• inputs from monitoring station data(point estimates) or air quality modeling or satellite data

• analyses focus on exposures PM2.5 and ground-level ozone (O3)

sources to concentrations?

sources → emissions → concentrations

• Emissions does not equal concentrations

• concentrations used for HIA

types of data used for exposure assessment

• personal measurements

• area or ambient measurements

• in the vicinity of the residence or other sites of activity

• surrogates of exposure (e.g. estimates of drinking water use)

• distance from site and duration of residence

• residence or employment in geographic area in reasonable proximity to site of exposure

• residence or employment in defined geographical area (e.g. country) of the site

air pollution data approach

a multi-pronged approach by integrating data from atmospheric models, ground-based monitors, and satellites- overcomes limitations of single data sources

strengths and limitations of computer models

simulate how pollutants are dispersed in the atmosphere and predict concentrations where data is scarce

strengths and limitations of fixed ground monitors

provide high quality, continuous data for specific locations and are considered the “gold standard” for accuracy

strengths and limitations of satellites

provide a broad, global perspective on air pollution, capturing data over vast regions where ground monitors are sparse or non-existant

popualtion (question, sources, considerations, focus)

• who is exposed to air pollution

• input from government census data, other demographic projections

• consider age and gender structure of population (most mortality studies apply to adults age > 30)

• apply population estimates from a single year for entire analysis

steps for calculating weighted average (exposure)

1. calculate total population

2. multiply each districts population by its pollution level

3. sum the products from step 2

4. divide the sum of the products by the total population

steps for calculating weighted average (RR)

1. assign the wights to each study (study 1 pop/total pop)

2. multiply each RR by its study weight

3. sum the weighted RR

Baseline health status (question, sources, considerations, focus)

• what is the underlying health status of the population

• inputs from government data

• consider morbidity and mortality

• this data is often the factor limiting spatial resolution in co-benefits analyses

health risk (question, sources, considerations, focus)

• how does exposure to air pollution increase risks to health?

• we understand these links through many observational cohort studies

• exposure response relationships from these studies connect cause and effect

what does the WHO ambient air quality guidelines tell us

• guidlines and interim targets for key pollutants

• limits set to protect public health and the environment

• used as a template for policymaking in many developing countries

• until recently, ambient air pollution and indoor air pollution were considered seperately