MIGRAINE: Health Effect of Air Pollution

Opinion / Articles
Air Pollution / Health - MIGRAINE: Health Effect of Air Pollution
Lela Gary, Keri Baxter
May 2005

A substantial number of Canadians suffer from severe headaches best diagnosed as “migraines”. According to a report in a longitudinal study in Canada it was estimated that migraines account for over 7 million lost working days annually. In US, migraines cause the loss of approximately 150 million work days per year at the estimated lost of labour cost of $13 billion.

What do we know?
Although studies on migraine have tested neurotoxic, immunological, cytotoxic and vascular theories, the link between air pollutants and headaches has not been acknowledged or validated widely by the medical profession. However, reports on the extent of exposure and geographic distance dominated by traffic-derived particles have been associated with migraine attacks. * (See Note)

Chemical sensitivity has been referred to as “Toxicant-Induced Loss of Tolerance” (TILT) which is characterized by a breakdown of tolerance resulting from acute or chronic exposure to chemicals.

The following studies have been found to corroborate our argument:

  • A work on Neurogenic Switching explains how neurogenic inflamation triggered by external chemical exposures can cause headaches.
  • A study attributing migraine to CO2 pollutant, it was suggested that when the amount of CO2 is lowered in an environment, then the frequency and severity of migraines decrease.
  • 3 studies reported that exposure to Carbon Monoxide (CO) affects neurogenic inflamation in disorders such as migraine headaches. Acute exposure to CO leads to brutal neurotoxicity with longer long- term effects.
  • The key findings in a study of the role of Nitric Oxide in vascular headache, indicate that NO is an important trigger for migraine. (Nitric oxide is a gas, part of NOX in automobile exhaust that plays a major role in photochemical smog).
  • A study in Turin, Italy showed clear correlation between increased headaches and increases in the CO and NO2 pollution index, with the possibility of synergistic interaction between the various pollutants.
  • Air ion depletion from industrial pollutants, traffic-engendered smog, and ducts of ventilation systems cause headache, loss of attention and somnolence.

What about the weather?
Migraines due to the weather has been attributed to temperature, humidity, thunderstorms, winds. Yet, correlation of similar weather conditions is not consistent among studies at different locations. The occurence of migraines in studies of metereological influences, barometric pressure, such as before a rise in humidity, approaching thunderstorms or windy weather, is increased. Pre-Chinook and high velocity wind days reported in a study done at the University of Calgary, Alberta is an example. Frequency of migraine attack is lower when barometric pressure is low, but when air is expanding often bringing rain, migraine frequencies decrease.

Considering the chemical intolerance of migraineurs to air pollutants, could the answer to this inconsistency be, that the accumulation of air pollutants differs at different locations?
Air quality index and the high concentration of pollutants in areas of high pressure was not correlated in the majority of metereological studies.
When slow sinking of air creates subsidence inversion, the buildup of high pressure forms and transports ground level ozone, associated with health problems and migraine.
Furthermore, the bioaccumulation of toxics in the organism and the extent of exposure to them, may create the toxicant-induced loss of tolerance that may explain the discrepancy of results in these studies in similar barometric conditions.

Elevated concentrations of ozone in Ontario, are usually in summer. Various treatments have been recommended in the studies of metereological factors and migraine. Considering the increase of migraines and other health problems associated with pollution, the best approach would be prevention by alleviating air pollution in our cities. The socio-economic impact is considerable.

*Note: The toxics benzene, PMs, PAH, ground-level ozone, CO2 and NOX are “primary pollutants”. VOC emissions and Nitrogen oxide (NOX) mainly include road vehicle transportation, have been linked to various health problems, increased hospital admissions and premature death. And yet 92% of deaths and hospitalizations linked to poor air quality occur on days when air quality is recorded “good” or “very good” according to the Auditor’s General report. The 2004 report further slams Ontario’s Environment Ministry for failing to adequately measure air pollution as the Ministry standardized only 18 of 76 high-priority pollutants, thus misrepresenting the health risks associated with air pollution.

Reference List:
Air Quality in Ontario, 2003 Report.Cooke, L. J.; Rose, M. S., and Becker, W. J. Chinook winds and migraine headache. Neurology. 2000 Jan 25; 54(2):302-7.
Gomersall, J. D. and Stuart, A. Variations in migraine attacks with changes in weather conditions. Int J Biometeorol. 1973 Sep; 17(3):285-99.
Handzel, ZT. Effects of environmental pollutants on airways, allergic imflamation and the immune response. Rev Environ Health 2000 Jul-Sep; 15(3):325-36
Kugler, J. and Laub, M. Headache determination by meteorotropic influences. Res Clin Stud Headache. 1978; 6:117-22.
Larmande, P.; Hubert, B.; Sorabella, A.; Montigny, E.; Belin, C., and Gourdon, D. [Influence of changes in climate and the calendar on the onset of a migraine crisis]. Rev Neurol (Paris).1996 Jan; 152(1):38-43.
Letters to the Editor: The Impact of Seasonal and Meteorological Conditions on the Incidence of Thrombotic Haemodialysis Shunt Occlusions. Thromb Haemost 2002; 88:1074-6
Lipton, R. B. Fair winds and foul headaches: risk factors and triggers of migraine. Neurology. 2000 Jan 25; 54(2):280-1.
Maybeck, H.F. Subsidence Inversions. Plymouth State College, Plymouth, New Hampshire Apr. 1996
McCarter, J. Auditor General of Ontario Report 2004 Meggs, WJ. Neurogenic inflamations and sensitivity to environmental chemicals. Environ Health Perspect 1993 Aug; 101(3)234-8
Miller, CS. The compelling anomaly of chemical intolerance. Ann NY Acad Sci 2001 Mar;933:1-23
Nattero G. Ourdoor Pollution and Headache. Headache 1996;(36)243-245
Osterman, P. O.; Lovstrand, K. G.; Lundberg, P. O.; Lundquist, S., and Muhr, C. Weekly headache periodicity and the effect of weather changes on headache. Int J Biometeorol. 1981 Mar; 25(1):39-45.
Nursall, A.S., Phillips, D.W. The effects of Weather on the Frequency and Severity of Migraine Headaches in Southwestern Ontario. Canadian Climate Centre Report 80-7 (unpublished manuscript, Environment Canada) 1980.
Piorecky, J.; Becker, W. J., and Rose, M. S. Effect of Chinook winds on the probability of migraine headache occurrence. Headache. 1997 Mar; 37(3):153-8.
Prince, P. B.; Rapoport, A. M.; Sheftell, F. D.; Tepper, S. J., and Bigal, M. E. The effect of weather on headache. Headache. 2004 Jun; 44(6):596-602.
Schwarzberg, MN. Carbon Dioxide level as a migraine threshold factor. Med Hypotheses,1993 Jul; 41(1) 35-6
Sulman, F. G. Migraine and headache due to weather and allied causes and its specific treatment. Ups J Med Sci Suppl. 1980; 31:41-4.
Townsend, C.L., Maynard, R.L Effects on health of prolonged exposure to low concentrations of carbon monoxide. Arch Neurol 2002; 59:1072-73
Wilkinson, M. and Woodrow, J. Migraine and weather. Headache. 1979 Nov; 19(7):375-8.

This is to thank the researchers for their acknowledgment and reference to our report on Migraine in their research: Air pollution and daily ED visits for migraine and headache in Edmonton, Canada.


The authors acknowledge Environment Canada for providing the air pollution data from the National Air Pollution Surveillance network. They appreciate the efforts of Ms Chris Houston from Information Services, Capital Health, and Ms Virginia Willis, from the Emergency Medicine Research Group (EMeRG), for securing these data and to Health Canada for funding data acquisition. Ms Lela Gary suggested the hypothesis.

It was not only our hypothesis, it was our Conviction that air pollution affects our health which prompted us to do our research on this issue.

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