Human health

Ozone depletion

The stratospheric ozone layer blocks a large part of the harmful UV radiation before it reaches the surface. Certain (mostly bromine and chlorine containing) substances however have the potential to destroy stratospheric ozone and thereby increase the amount of radiation that reaches the surface which causes damage to ‘Human Health’.

 

Cause-effect pathway

 

After emission to air ozone depleting substances (ODS) spread throughout the atmosphere and eventually they will end up in the stratosphere where their chlorine and bromine groups interact with and destroy the ozone.

 

Modeling approach

 

A marginal approach is used to calculate the effect factors.  Semi-empirical data (based on well recorded historic emissions of ozone depleting substance) is used to determine the effect of the different substances on the EESC (Equivalent Effective Stratospheric Chlorine). The EESC is a measure for how much stratospheric ozone can be destroyed. By calculating the resulting (optical) ozone layer thickness the amount of radiation that reaches the earth can be estimated. The increase in skin cancer (and cataract) can be determined from the amount of radiation, however this is dependent on the amount of skin pigment the population has (more pigment means less chance of getting skin cancer).  Whether or not exposure to UV radiation causes cataract is uncertain.

 

 

Value choices

 

A number of choices have been made for the calculation of the characterization factors, namely:

  • The time horizon over which effects are assessed

  • Whether or not to include cataract

 

Core CF

Extended CF (in addition to core)

Time horizon

100 years

100 years - Infinite

Included effects

Skin cancer

Cataract

 

 

Spatial variability

 

The emitted ozone depleting substances will spread throughout the entire atmosphere before they have an effect on the ozone layer. In fact, a time period of three years is included to take into account the time needed for a ODS to transport all the way to the stratosphere. By this time the spread is global and there is no need to correct for different emission locations.

 

 

Characterisation factors

 

The following equation can be used to calculate the characterisation factors (CF):

 

CFx,TH = ODPx,TH ∙ EFCFC-11,TH

 

where ODP stands for ozone depletion potential of substance x and EF stands for effect factor of the reference substance CFC-11 for time horizon TH.

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