MLHU - Health Status Resource

Couple walking in park together

The physical environment in which we live, work, and play is an important contributor to our health, as well as the overall health of the community. Ontario public health units have a mandate to monitor aspects of the environment that may impact health, including air quality, extreme weather, the safety of food, and insects and animals that may transmit diseases to humans.

Everyone is exposed to air pollution, and regardless of the amount, it can substantially impact health. It was estimated that in Canada, 14,600 premature deaths occur each year due to air pollution.1 Another Canadian study projected that from 2008 and 2031, the direct (e.g., health care costs) and indirect costs (e.g., lost productivity) of air pollution would exceed $257 million (2006 dollars).2

Although the Middlesex-London region experiences air pollution from both local and transboundary sources, outdoor air quality did not routinely pose an increased risk to human health between 2015 and 2018. During the four-year period, there were no days in London where the Air Quality Health Index (AQHI) was classified as high or very high, and there were no Smog and Air Health Advisories (SAHA) issued across the entire time frame. The annual average concentrations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) both decreased over time in London. However, between 2008 and 2017 the local annual average concentration of ground-level ozone (O3) fluctuated, and generally increased.

Extremes in outdoor air temperature can also play a role in human health. In addition to additional burden on the health care system, extreme hot and cold weather have both have been associated with increased mortality.3 In the 10 years from 2009 to 2018, the annual number of heat or cold weather notifications issued for Middlesex-London ranged from zero to eight per year for each. However, the total number of days the region was affected by cold weather was more than 50% greater than the number of days with extreme heat.

In Canada, it has been estimated that about four million people become ill each year due to a food-borne infections, resulting in over 11,000 hospitalizations and more than 230 deaths.4 While food-borne illnesses can be potentially spread in any setting where food is stored and prepared, including in homes, an important component of a healthy environment is ensuring the safety of food served by dining establishments, so that food-borne illnesses and outbreaks do not spread in the community.

In each year from 2015 to 2018, the proportion of public food premises in Middlesex-London confirmed as the source of food-borne illness or outbreaks was low, at five or fewer each year, corresponding to 0.3% or lower annually. The majority of dining establishments in the region, more than 88%, had food handlers who demonstrated safe food-handling practices. While not a legislated requirement, having a documented food safety management plan is a best practice for food premises. While many premises have processes in place to monitor safe food handling, between 2015 and 2018 less than 15% of inspected premises had formally documented a food safety management plan, and the proportion gradually decreased in each of the four years.

Monitoring insects and animals that may carry diseases and to which the community may be exposed is also an important part of a healthy environment. In each year between 2005 and 2018, the number of mosquito pools in Middlesex-London that tested positive for West Nile virus fluctuated between zero and 17. At the same time, the number of West Nile virus human cases reported among Middlesex-London residents was low, and varied each year. Although 2012 and 2018 were the years in which both the number of West Nile virus positive mosquito pools and reported human cases were highest in Middlesex-London, there did not appear to be a strong association between the two outside those years. Further, there did not appear to be any sustained year over year increases or decreases in either positive pools or human cases.

The most recent human rabies case due to animal exposures in Ontario was reported in 1967.5 Although rare, human rabies infections are almost always fatal. Public health units carry out an important role in monitoring the prevalence of rabies among animals in the region, as well as investigating possible rabies exposures and recommending prophylactic measures when necessary. Between 2014 and 2018, the number of animals confirmed with rabies in Middlesex-London was low, suggesting that the risk to the community was similarly low. The number of Middlesex-London residents assessed for possible rabies exposure after being bitten or scratched by an animal steadily increased between 2010 and 2018, and post-exposure prophylaxis was recommended for 12% of investigations during that time period.


1.Health Canada. Health impacts of air pollution in Canada: estimates of morbidity and premature mortality outcomes, 2019 report [Internet]. Ottawa (ON): Health Canada; 2019 Jun [cited 2019 Nov 4]. 38 p. Available from:

2.Canadian Medical Association. No breathing room: national illness costs of air pollution [Internet]. Ottawa (ON): Canadian Medical Association; 2008 Aug [cited 2019 Oct 21]. 45 p. Available from:

3.Chen H, Wang J, Li Q, Yagouti A, Lavigne E, Foty R, Burnett RT, Villeneuve PJ, Cakmak S, Copes R. Assessment of the effect of cold and hot temperatures on mortality in Ontario, Canada: a population-based study. CMAJ Open [Internet]. 2016 Feb 2 [cited 2019 Nov 4];4(1):E48-58. Available from: doi: 10.9778/cmajo.20150111

4.Government of Canada [Internet]. Ottawa (ON): Government of Canada; [modified 2019 Nov 9]. Yearly food-borne illness estimates for Canada; [modified 2016 Jul 5; cited 2019 Nov 4]; [about 3 screens]. Available from:

5.Ontario Agency for Health Protection and Promotion (Public Health Ontario). Rabies [Internet]. Toronto ON: Ontario Agency for Health Protection and Promotion’ [cited 2019 Nov 13]. [about 2 screens]. Available from:

Last modified on: November 19, 2019