ALMOST everybody in Hongkong has experienced the unpleasant effects of pollution, whether it be head-pounding pile driving, ear-splitting karaoke in the flat next-door, or black smoky fumes from a passing lorry. Suffering in silence, however, is not the only way to dealing with it. Complaining can bring results. Although the system isn't perfect, there are ways to bring at least some offenders to justice. Last year 5,860 people griped to the Environmental Protection Department's (EPD) hotline, with almost nine-out-of-10 callers complaining about air and noise pollution. The strength of the EPD's follow-up depended on how much information complainants provided and whether there were laws to deal with the problem, but the department investigated all cases, according to Mr Elvis Au Wai-kwong, who handles the complaints. Mr Au said people could complain anonymously, but the EPD needed specific information on the location, time of offence and nature and source of the problem. For instance, if a restaurant ventilation system was causing annoyance in the evening, the complainant should provide the location of the vent, the name of the restaurant and precise times when it was a problem, so the EPD could investigate. If any of that information is missing, the EPD will try to investigate but the chance of success is less. While the investigation process and eventual prosecution can take weeks or months, depending on staff resources and the nature of the complaint, more immediate relief can be found through the police, at least for noise pollution. ''A lot of people lodge complaints about neighbourhood noise. They think it's up to the EPD to enforce, but it should be the police because they can take immediate action,'' Mr Au said. Local police stations can step in if mechanical construction equipment is operated after 7pm or there is any type of loud noise after 11pm. Some loud domestic noise also is banned during the day, including that from musical instruments, karaoke, animals and birds, loudspeakers, trade or business in the flat, games such as mahjong and air-conditioners. Air pollution problems are less straightforward and harder to act against. Black smoke from vehicles is by far the biggest source of complaint, accounting for 49 per cent of the air pollution total. But a complaint isn't necessarily going to stop it. The EPD will issue warning letters to offenders after verifying that the vehicle information from a complainant is correct. But only trained and authorised ''spotters'', of which there are a few hundred, have the authority to order the vehicle to have a smoke emission test and correct the problem. ''Some may abuse the system and then we have to spend time chasing the names,'' Mr Au said. Air pollution from factories, restaurants and other sources is easier to control because the EPD can send an agent to the sites to measure the smoke, and prosecute if it is too dirty. ''Air and noise are the most obvious types of pollution and they are immediately felt by the public in their neighbourhood. The other problems are not affecting their daily life, although it doesn't mean they're not serious,'' he said. Not all pollution problems are handled by the EPD or police. These are referred to other departments, particularly the Urban Services Department and Regional Services Department which deal with littering, rubbish collection and other public hygiene issues. The EPD's hotline, 838-3111, is manned during office hours with a recorded message at night, as is the Urban Services hotline, 868-0000. The Regional Services hotline, 414-5555, is manned from 8am to midnight, after which there is a recording. If you have an environmental project of interest or wish to call to attention to an environmental problem in your neighbourhood, please fax the information to Ecowatch on 811-1278, or mail it care of the South China Morning Post.