Recent research has revealed that exposure to high pollution levels can increase people's susceptibility to stroke.
In fact scientists in Japan have found that the risk of stroke from pollution can more than double by the hour.
Currently breathing and heart problems are associated with the average daily amount of air pollution rather than variations in hourly levels.
The findings of the study are published in Occupational and Environmental Medicine. The researchers collected data on stroke deaths among people of ages 65 years and older between January 1990 and December 1994 in 13 cities.
In addition they also monitored levels of common air pollutants such as particulate matter, nitrogen dioxide and photochemical oxidants were monitored hourly at various sites.
Study of the two sets of data revealed a a pattern for a stroke called intracerebral hemorrhage where a blood vessel breaks and bursts open inside the brain during the warmer months between April and September.
This revealed that high hourly rate of particulate matter about two hours before death was associated with an increase in the risk of stroke following a burst blood vessel in the brain by over two times.
These findings were consistent irrespective of the average daily level of air pollutants.
However similar results were not seen in ischaemic stroke where the arteries of the brain become thickened and narrowed as a result of fatty deposits.
According to the researchers this could be attributed to the time lag between the start of this type of stroke and death is comparatively longer than that for a bleed into the brain.
Environmental epidemiologist Dr Shin Yamazaki, of Kyoto University, said: "One possibility is the interval from stroke onset to death is much longer, or much more variable, for ischaemic stroke than for intracerebral haemorrhage.
"Another possibility involves the effects of inhaled particles on blood pressure and the fact hypertension is a risk for intracerebral haemorrhage.
"Laboratory findings suggest exposure to fine particles can increase blood pressure. In other studies more untreated hypertensive patients had cerebral haemorrhage than had other types of stroke and blood pressure is more strongly associated with haemorrhagic stroke than with ischaemic stroke."
Previous research had revealed that the effects of air pollution make their presence very quickly on the body with inhaled particles measurable in the blood within 60 seconds. Peak levels can stay in the blood for up to an hour.
These revelations prompted scientists to suggest that preventive measures should take into account the average hourly measures rather than just average daily measures alone.
Said Dr Yamazaki: "To help prevent stroke related death due to air pollution air quality standards for particulate matter should be based not only on 24-hour mean concentrations but also on hourly data."