There's a fly in the ointment of solar-powered LED lighting

Solar power has the potential to transform the lives of millions of Africans. But there's a big problem: disease-carrying bugs. Mark Booth, senior lecturer in epidemiology at Durham University, reports.

Household air pollution is estimated to kill more than 500,000 people in Africa each year. Through solar energy, people can stop using dirty and extremely polluting fuels like kerosene in their homes. But with domestic solar energy comes an unintended consequence. When the light bulbs are switched on, they can attract disease carrying bugs.

Given the health threats of kerosene and other indoor pollutants, a number of initiatives are driving the use of solar power for domestic uses. Organisations associated with the UN Sustainable Energy For All initiative are promoting various programmes.

And donors are also moving into this space. One example is the EnergyAfrica campaign being driven by UK’s Department for International Development, or DFID. Its focus is on domestic solar, providing individual householders with systems to power small electrical devices in the home. This mainly involves light bulbs.

The irradiation potential for sunshine to provide this form of clean energy in Africa is substantial. There will undoubtedly be enormous health benefits provided that people switch from kerosene and other so-called dirty fuels, instead of adding solar to the mix of energy types they use.


So what's the problem?

Let’s temporarily set aside the potential problems of financing and sustainability for individual householders unused to looking after complete solar systems. There is one glaring issue with providing electrical light into otherwise non-improved residences like mud huts with corrugated iron roofs: flying insects.

Many different types of insects are attracted to light sources. This is either in search of a mate or after taking a meal. Many insects attracted to lights may be harmless, but key species are known vectors of disease that affect both humans and animals. These include:

Ironically, it is low-energy LED light bulbs that are the most attractive due to the fact that they emit more blue light. This is such a major issue that attempts are underway to tune LEDs so that they attract a smaller number of flying insects.


Artificial light + human odours + evolution = trouble

Mosquitoes are not just attracted to light. They also seek out human skin due to the CO2 released by our bodies when we breathe, and are attracted to chemicals released by skin bacteria.

Historically, this may not have been a major issue because mosquitoes tend to feed after midnight. But mosquito populations may have evolved to seek blood-meals earlier in the night due to the selective pressure of bed nets. In addition, the efficiency of transmission from humans to mosquitoes may have increased over recent decades. This again is due to the pressure of control measures against the parasite.

So what might happen if the introduction of artificial light, using low-energy LEDs, is combined with other interventions?

Research is still at an early stage. On the one hand, modern housing may reduce the risk of malaria. But there is already some epidemiological evidence that electrification of community buildings and neighbourhoods may accidentally increase the risk of malaria and other diseases.

Some of these effects may be directly as a result of lights attracting vectors of disease to places where humans are present. Alternatively, the vectors may not be attracted to light itself but to humans who are undertaking domestic and economic activities near to a source of artificial light. This may be happening even as the harmful effects of particulates from kerosene lamps are reduced.


Joining the dots

To find solutions to this double-edged sword we can first turn to the field of Evolutionary Medicine. This considers how evolutionary processes shape our ability to combat disease. Research in this field can be combined with an integrated approach involving sustainable buildings, and sociotechnical research to tackle both energy and health issues simultaneously.

At the heart of that idea is the fact that solar power, when integrated into modern, energy-efficient buildings, can be used entirely off grid to bring electricity to hundreds of millions of people in Africa who lack access to energy. Many of these people live in areas where vector borne diseases are common.

Such an integrated approach needs careful planning and will not provide solutions at the same pace as providing small-scale solar systems to individual householders. This is probably why DFID is now behind small-scale solar. The technology has overcome historic barriers of affordability, availability and energy storage and can be installed into otherwise unimproved residences.

DFID is keen to open up the market to businesses in the solar sector. I am keen to ensure that the evidence base keeps on building so that the public, private and civil sectors are informed about the consequences and impact of their activities.

More generally, forewarned is forearmed, and by conducting research and examining the evidence ahead of wide-scale implementation, we can generate testable hypotheses and combine basic, applied, operational and implementation research to greater effect.

Mark Booth is senior lecturer in epidemiology at Durham University

This article was originally published on The Conversation. Read the original article.

Picture: Raymond Gilford

Comments 1

In my experience, nothing attracts sand fleas better than a propane lamp. The question of insect attraction is by no means cut and dried or simple: the fact is that various insects are attracted to various spectra (phototactic action spectra) so there is no such thing as a bug-free light - some species of moth and midge are actively attracted to old school yellow bug lights. Mosquitos as we know can readily find one in the dark. Research indicates that exclusive of old school mercury lamps and incandescent lamps, the PAS for insects studied is nearly flat (i.e. no ideal SPD). Possibly there is a least effective illumination relative to insect attraction based on local insect populations but not any that is ineffective: since it's an issue of relativity, the only real comparison is between the efficacy of the various available light sources and, given the complexity of the problem, a weighted risk analysis; threat levels may also vary according to levels of inoculation against the spectrum of diseases for which insects are a vector. However, any such epidemiology without ANOVA in the face of many factors is speculation. The best available information is that at least plant seeking insects exhibit preferential phototaxis for UV light (UV is not blue) while several insects use IR signalling for mating purposes (moth to a flame, etc).

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