lahore, dec 29: the period of winter fog is increasing ac- cording to a study published this week by the pakistan space and upper atmosphere research commission (suparco). the findings were also corro- borated by punjab university’s dr ghazala nasim and dr m nawaz chaudhry, both members of the provincial environment protection department’s ‘climate change cell’. the study found that fog ag- gravated environmental prob- lems and had adverse impacts on human health. “although fog formulation re- lates to meterological conditions, it is becoming denser and per- sisting for longer duration owing to high level of chemical species in fine particulate matter or aer- osols such as sulphate,” conclu- ded b. ghauri, the author of the suparco report. the report said increased load of particulate matter in lahore were contributing to asthma. winter and spring levels of pm2.5 (particulate matter with a diameter of less than 2.5 micro- metres) peak at 35 µg/m3 (micro- grams per metre cubed) was 14 times higher than the prescribed limits set by the world health organisation. until 10 years ago, the period of winter fog in punjab used to last about five days but this peri- od has steadily grown and the fog period for the winter of 2007-08 was an unusually high 17 days, according dr m nawaz ch, a pro- fessor at pu’s college of earth and environmental sciences. suparco’s study carried out from 1999 to the present at its field office in lahore showed high pollutant levels in all field samples of so4 from 4 to 141 µg/m3 and no3 from 3 to 74.5 µg/m3. concentrations of black car- bon (bc) determined every 5 mi- nutes at lahore from nov 2005 to jan 31, 2007 were among the highest urban values worldwide, ranging from 5 to 110 µg/m3 with a mean of 21.7 µg/m3. the study said a high concentration of soot over india and china was respon- sible for a trend toward in- creased flooding in the south and drought in the north. the light-absorbing effect of soot is also directly affecting plant growth in pakistan, accord- ing to dr ghazala nasim, who is an assistant professor at pu’s institute of mycology and plant pathology. dr nawaz suggested that a cost-benefit analysis was re- quired to determine whether ground control at lahore airport receive “category-iii” instru- ment landing to guide planes to land during thick fog, if the peri- od of fog in punjab continued to grow. meanwhile, thick fog contin- ued to disrupt daily life for the third day running on monday in lahore, gujranwala, faisalabad, multan, bahawalpur, sargodha, jhelum and muzaffargarh districts, though there was a marginal improvement in visibility. according to meteorological department officials, visibility in lahore at 5am was 30m as op- posed to 20m on sunday. visibility at 8pm was 800m, up from 500m the previous day. the maximum temperature rose from sunday’s 13 degrees celsius to 15.2 degrees celsius, and the minimum temperature was 6.8 degrees celsius with 93 per cent humidity in the morn- ing and 77 per cent humidity in the evening, again down from the previous evening. trains were delayed by two to eight hours, while flights to and from lahore airport continued to face severe disruptions, accord- ing to caa officials. according to a spokesman for the national highways and motorways, traffic on the motor- way between lahore and islamabad and lahore and faisalabad was suspended.