Environmental burden of disease calculation

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Environmental burden of disease calculation

This chapter provides information about methods to calculate the environmental burden of disease, and the assumptions and choices that need to be made. Table 2-1 provides an overview of these baseline assumptions underlying the calculations as performed in the EBoDE project. The remainder of this chapter describes the specific models used for calculating the EBD and explains the different parameters and data used.

TABLE 2-1. Baseline facts and assumptions underlying environmental burden of disease calculations as carried out in the EBoDE project.

Parameter of assumptions	Choise made	Motivation	Remarks
Year	2004	Most redcent year with relatively good data availability	Exposure trends were evaluated till 2010 for a qualitative policy analysis
Environmental stressors	Benzene, dioxins (including furans and dioxin-like PCBs), second-hand smoke, formaldehyde, lead, noise, ozone, particulate matter (PM) and radon
Countries	Belgium, Finland, France, Germany, Italy and the Netherlands	Integration of national projects	EBoDE working group and methodology is open for other countries
Age weighing & discounting	Main results without discounting and age-weighing; alternative results with discounting (3%) and age-weighing (standard)		Ethical reasons. Supplementary discounted and age-weighed results presented for comparability with WHO estimates
Standard Life Expectancy	80 years for men and 82.5 for women	Comparability with WHO estimates
Lag time	Calculations carried out with and without lag times	For certain diseases there is a relatively long lag between exposure and the effect. When using discounting, the lag should be accounted for	Lag times are based on author judgement and serve as rough estimates
Uncertainty analyses	Qualitative and partly quantitative	It is essential to assess whether the substantial inherent uncertainties affect the order of magnitude of the results or the ranking of stressors	Data availability and limited resources allowed only for qualitative approach. Additional quantitative analyses are recommended as a part of follow-up research

Basic calculation of the environmental burden of disease

The DALY measures health gaps (i.e. years of life lost due to death or disability) as opposed to health expectancies. It measures the difference between a current situation and an ideal or alternative situation. The DALY combines the time lived with disability and the time lost due to premature mortality in one measure:

DALY = YLL + YLD

where: YLL = Years of Life Lost due to premature mortality. YLD = Years Lost due to Disability.

Years of Life Lost (YLL) in a case of individual death is calculated as the difference between the standard life expectancy at the age of death and the actual age at death. When population data is tabulated for age categories, YLL can be calculated as:

L = LE (agedeath, gender) -agedeath The basic formula for calculating the population-wide YLL is: YLL = N x L

where: LE(age,gender) = life-expectancy at age of death, accounting for gender agedeath = age at death N = number of deaths in a given age category L = remaining years to standard life expectancy at age of death (in years).

Methods for calculating YLL are further described in section Years of Life Lost, co-morbidity and multi-causality

To estimate the Years Lost due to Disability (YLD), the number of disability cases is multiplied by the average duration of the disease and a disability weight (see further discussion below). The basic formula is:

YLD = n x DW x L

where: YLD = Years Lost due to Disability n = number of incident cases. DW = disability weight. L = average duration of disability (years)

The formulas above describe undiscounted, non-weighted DALYs. DALYs are sometimes attributed a discounting rate, and weightings according to age, in which case the formulas become more complex. These so-called social preferences are discussed in section 2.3.