Most people in northern Thailand have been affected by the thick layer of toxic smog blanketing parts of their provinces, according to a survey by the National Institute of Development Administration, or Nida Poll.

The poll was conducted on 1,253 people in the nine northern provinces of Chiang Mai, Chiang Rai, Lamphun, Mae Hong Son, Nan, Lampang, Phayao, Phrae and Tak on April 4-5.

A majority -- 82.52% -- of the respondents said they have been affected by toxic particulates, with 36.47% saying the adverse effect of the smog on them was very high, 20.51% rather high, and 25.54% moderately high. Only 8.22% said they have been little affected and 9.26% not affected at all.

Of those affected, 60.51% said they have suffered from symptoms of a cold with irritated and running noses; 49.34% from breathing difficulties; 48.11% from eye irritation; 39.23% from coughing and sore throats; 7.12% from rashes all over their bodies; 2.37% from reduced visibility; and 0.18% were uncertain.

Asked what protective measures they have taken, 83.73% said they have resorted to wearing face masks; 29.02% have avoided leaving their homes; 21.64% have kept the doors and windows of their homes closed; 10.64% have refrained from outdoor exercise and have drunk a lot of water; 6.16% have used fans and air purifiers; 5.63% have refrained from burning garbage; 3.96% have cleaned their air-conditioners; 1.5% have refrained from smoking; 0.7% have travelled to other provinces not affected by smog; 0.44% have reduced their use of private cars; and 2.81% have taken other measures, including spraying water around their houses, wearing eyeglasses and not doing anything at all.

Most of the respondents -- 87.95% -- said they have not sought medical treatment during the prevalence of the toxic smog. Only 10.82% said they have sought treatment for smog-related sickness, while 1.23% said they have done so for other reasons.

Asked what expenses they have incurred seeking medical treatment as a result of the smog, 45.53% said they have received free treatment; 26.83%  have spent less than 500 baht; 13.01% between 501-1,000 baht; 2.24% between 1,001-1,500 baht; 6.50% between 1,501-2,000 baht; and 5.69% more than 2,000 baht.