IEHIAS scenarios: example for UVR and skin cancer

The text on this page is taken from an equivalent page of the IEHIAS-project.

As part of the EU-funded INTARESE project, which contributed to the development of this Toolbox, a case study was conducted to assess the health impacts of changing exposures to ultraviolet ratiation (UVR).

The case study explored the effects of changing exposure to ambient ultraviolet radiation (UVR) on malignant melanoma (CMM), basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), accounting for the changes in stratospheric ozone (due to decreasing emission of ozone depletng substancesand increasing emissions of CH₄ and N₂O. It also took account of future demographic change.

In order to deal with uncertainties related to future emissions and future demographic developments, two different sets of scenarios were applied.

Factors influencing (future) stratospheric ozone levels

The status of the ozone layer (and therefore ground level UVR) is influenced by emissions of ODS (regulated by the Montreal Protocol), but also by emissions of methane (CH₄) and nitrous oxide (N₂O).

The international mechanism for protecting the ozone layer is the “Montreal Protocol on Substances That Deplete the Ozone Layer”, which came into force in 1989, and its subsequent amendments (UNEP 2006). Over the next few decades, the benefits of these measures will become apparent as compliance has been high. Overall, the Montreal Protocol is seen as the most successful international environmental agreement to date. The production of chlorofluorocarbons (CFCs), halons and methylbromide, the most harmful ozone depleting substances, are now phased out worldwide. The concentrations of these gases in the atmosphere is anticipated to reduce over the next decades. As a result, ozone levels are expected to increase in the coming decades, although the evolution will also depend on the changing climate system (IPCC 2005). However, it will probably take several decades until atmospheric ODS concentrations will fall below pre-1980 levels.

CH4 acts as a precursor of the radicals that determine ozone chemistry. In addition, CH₄ is the primary mechanisms for the conversion of reactive Cl to the unreactive HCl, affecting the efficiency of chlorine-driven ozone loss (IPCC 2005). The oxidation of CH4 increases water vapour and, subsequently, ozone losses in the HOx catalytic cycle in the upper stratosphere and lower mesosphere. In the troposphere and lower stratosphere, ozone is increased because oxidation of CH₄ catalyzed by NOx produces ozone.

N2O acts as a precursor of the radicals that determine ozone chemistry (IPCC 2005). In the mid to upper stratosphere, N2O induces reduction of ozone. Increases in N₂O lead to increases in the NOx catalytic loss cycle for ozone in the mid to upper stratosphere, because N2O decomposes to form NOx in the stratosphere (N₂O induced reduction of ozone).

Future scenarios (2030, 2050): IPCC SRES-A2 and SRES-B1

The scenarios used in this study are based on the SRES- scenarios by the IPCC (2000) (Box 1). The SRES scenarios are widely used for climate change assessments. They quantify the emissions of greenhouse gases (including CH4 and N2O) and ODS over the coming century, and their key drivers (population projections, economic growth, energy choices). The time horizon for the SRES-scenario is up to 2100. The WP3.7-UVR assessment primarily focuses on baseline (2000), 2030 and 2050. Besides developments in stratospheric ozone, the ageing of the population is expected to have an effect on future skin cancer in the population as well (UVR-related skin cancer incidence and mortality is higher at older ages).

Box 1: The IPCC SRES-Scenarios

The SRES scenario effort of the IPCC (2000) was developed, via a broad consultative process, for estimating emissions of greenhouse gases over the coming century, taking into account input and perspectives from a wide, interdisciplinary research community. The resulting Special Report on Emission Scenarios (SRES) explores the global and regional dynamics that may result from changes regarding population, economy, technology, energy use, and agriculture (land use). The scenarios are intended to exclude catastrophic futures. The distinction between classes of scenarios was broadly structured by defining them ex ante along two dimensions The first dimension relates to the extent both of economic convergence and of social and cultural interactions across regions; the second has to do with the balance between economic objectives and environmental and equity objectives. This resulted in the creation of four scenario ‘families’ or ‘clusters’. Whereas the ‘A’ storylines (A1 and A2) emphasise economic development and leave only a subsidiary role for environmental and social concerns, the ‘B’ storylines (B1 and B2) reverse these priorities. The ‘1’ storylines (A1 and B1) emphasises successful economic convergence and social and cultural interaction across regions, while the ‘2’ storylines (A2 and B2) focus on diverse regional developments. For detailed information about the SRES scenarios, we refer to the original source. A1: Rapid market-driven growth, with convergence in incomes and culture. A2: Self-reliance and preservation of local identities; fragmented economic and technological development. B1: Convergent world with rapid changes in economic structures and emphasis on global solutions to sustainability. B2: Local solutions to economic, social, and environmental sustainability

Of the four SRES-scenarios, WP3.7-UVR explored SRES-A2 and SRES-B1. For our assessment, several scenario characteristics are important (Table 1):

Table 1: Main characteristics of the SRES A2 and B1 scenarios, relevant for UVR assessment (IPCC 2000)

IPCC scenario	SRES-A2	SRES-B1
ODS emission	decreasing trend -same as B1	decreasing trend- same as A2
CH4 emissions	higher increase	lower increase
N2Oemissions	higher increase	lower increase
Population	higher growth	lower growth
Age structure	slower ageing	faster ageing

UVR exposure under SRES-A2 and SRES-B1.

Hence, the WP3.7UVR-exposure scenarios are based on the IPCC emission scenarios (resulting from the SRES-storylines) and associated emission modelling and resulting atmospheric concentrations. For more information we refer to the IPCC data and publications:

• IPCC Special Report on Emissions Scenarios
• SRES Final Data Breakdown
• Climate Change 2001 - IPCC Third Assessment Report

Based on these (future) atmospheric concentrations of ODS, CH₄ and N₂O, The University of Oslo has calculated total ozone columns for the SRES-A2 and SRES-B1 scenarios (2000, 2030, 2050): the resulting ozone fields for SRES-A2 and SRES-B1 were estimated (personal communication with B. Rognerrud). Within WP3.7-UVR, these have been translated into ambient UVR levels for Rome, London and Helsinki. The results show that UVR exposures are higher (and ozone recovery slower) in SRES-B1 compared to SRES-A2. The larger increase in ozone column in SRES-A2 can probably be explained by the higher abundance of CH4in this scenario.

Table 2: WP3.7 modelled ambient UVR: average erythemal daily dose.

City	London	Rome	Helsinki
Baseline	1234	1747	899
B1 2030	1202	1701	877
A2 2030	1196	1691	873
B1 2050	1186	1679	866
A2 2050	1176	1663	859

See also

• Changing ambient UVR and future melanoma skin cancer
• Changing ambient UVR and future non-melanoma skin cancer

References

• IPCC 2000 Emissions scenarios. A special report of Working Group of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press.
• IPCC 2005 Special report on safeguarding the ozone layer and the global climate system: issues related to hydrofluorocarbons and perfluorocarbons. Cambridge: Cambridge University Press.
• IPCC 2007 Climate Change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. (Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Tignor, K. B., and Miller, H. L., eds.) Cambridge: Cambridge University Press.
• UNEP 2006 Handbook for the Montreal Protocol on substances that deplete the ozone layer. 7th edition. Nairobi: United Nations Environmental Programme, Ozone Secretariat.