TB Infection Control
germicidal effects of sunlight
I have been asked by a number of people about the beneficial effects of sunlight on the interruption of transmission of TB. Is there any significant direct germicidal effect of regular sunlight on TB or are the benefits from sunlight due to the production of vitamin D and its effect on the immune system and its ability to combat TB. Does having the sunlight filtered through glass windows negate any/all benefits? If it is UVc that is the germicidal wave length (which if I understand correctly is blocked by the atmosphere) why is it now being recommended that water be sterilized by being exposed to sunlight? Any clarification would be much appreciated.
Many thanks,
Maria Pia
Maria Pia Sanchez, FNP, MS, MPH
Principal Technical Advisor
Emerging Infectious Diseases
Management Sciences for Health
Edward Nardell, MD
The peak germicidal effect due to DNA damage is at 260 nm UV, close to
UV C 254 nm of germicidal lamps, whereas sunlight is composed entirely
of longer wavelength UV A and B. No 254 nm UV gets through the Earth's
atmosphere. However, the carcinogenic effect of sunlight is also due to
DNA damage, so clearly sunlight has significant germicidal potential
given its intensity and its inherent greater penetrating ability. I have
not seen any quantification of the germicidal effect of sunlight but it
is safe to assume that airborne bacteria would likely be killed by
intense sunlight.
Edward A. Nardell, MD
Associate Professor
Harvard Medical School (Medicine; Global Health and Social Medicine)
Harvard School of Public Health (Environmental Health; Immunology and
Infectious Diseases)
Brigham and Women's Hospital
Division of Global Health Equity
Boston, MA 02115
3:36 AM, 25 Apr 2009 | Permalink
Maria Pia Sanchez, FNP, MS, MPH
Thanks Ed. Can you clarify for us whether window glass interferes with this process?
2:49 AM, 28 Apr 2009 | Permalink