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Avian influenza, commonly known as bird flu, is an infectious disease caused by influenza A viruses that primarily infect birds. Avian influenza viruses are classified according to their characteristics and the species they infect. Most avian influenza viruses do not infect humans, but some viruses can occasionally cross the species barrier and cause human infections.Human infection with avian influenza was first recognized in Hong Kong in 1997, when highly pathogenic H5N1 viruses infected humans. Since then, H5N1 and other avian influenza viruses have caused sporadic human infections in different parts of the world. Beginning in 2020, a major global spread of highly pathogenic H5N1 among wild birds and poultry also resulted in infections in a growing number of mammals. Human infections remain uncommon, but people who have close or prolonged contact with infected birds or mammals can be at increased risk.Avian influenza viruses can infect many species of birds and some mammals, including poultry and wild birds, as well as mammals such as foxes, skunks, seals, and other animals. Wild birds can carry and spread some avian influenza viruses, sometimes with few or no obvious symptoms, while highly pathogenic strains can cause severe disease and death in poultry and some wild birds. Viruses can spread among animals through respiratory secretions, saliva, feces, and contaminated environments. People can become infected primarily through close contact with infected animals or contaminated environments. Human-to-human transmission of currently circulating avian influenza viruses is considered uncommon, although influenza viruses can change and therefore continue to be closely monitored. Properly cooked poultry [...]

The pH value, or hydrogen-ion activity, is a scale used to describe the acidity or alkalinity of an aqueous solution. More precisely, pH is related to the activity of hydrogen ions in the solution and is commonly expressed on a scale based on the negative logarithm of hydrogen-ion activity.At 25°C, a pH below 7 is generally described as acidic, a pH above 7 as alkaline or basic, and a pH of 7 as neutral. The neutral point can vary with temperature, so pH 7 is not universally neutral at every temperature.There are several methods for measuring pH. Acid-base indicators change color over particular pH ranges, allowing an approximate pH to be determined. pH test strips work on a similar principle and are available in different ranges and degrees of precision. For more accurate measurements, a pH meter uses a pH-sensitive electrode, commonly a glass electrode, to measure the electrical potential associated with hydrogen-ion activity. Properly calibrated laboratory pH meters can provide measurements to considerably greater precision than is normally required for household or field applications. Acid-base titration can also be used to determine the concentration of an acid or base and its neutralization capacity, although titration is not normally a direct method of measuring pH.Because pH affects chemical and biological processes, controlling it is important in many fields:In medicine, the pH of arterial blood in a healthy person is normally maintained at approximately 7.35 to 7.45. Significant deviations from this range can indicate acid-base disorders and may require medical attention. The pH of saliva can [...]

Secondhand smoke is the smoke inhaled when we are in close proximity to a smoker. Secondhand smoke is harmful to both nonsmokers and smokers. According to statistics and analyses, secondhand smoke contains more than 4,000 chemicals, at least 50 of which are carcinogenic; Non-smokers who live with smokers have a higher risk of developing heart disease; children living with smokers are more likely to develop bronchitis and pneumonia; and children—especially infants—who live with smokers are at a higher risk of developing illnesses such as colds, respiratory infections, and ear infections. Compared to the amount inhaled by active smokers, secondhand smoke contains higher levels of carbon monoxide and tar. It contains higher levels of ammonia, benzene, and various other hazardous chemicals. Advertisements for low-tar and low-nicotine cigarettes do not mean they are safer, as they release the same amount of toxic chemicals into the air. Smokers have a higher risk of miscarriage, stillbirth, premature birth, and giving birth to low-birth-weight infants. Therefore, even if we do not smoke ourselves, we still need smoke-free environments in offices, restaurants, and other public places. By Michael Chiu, MWS, CI Previously published in Ming Pao Daily News

Microorganisms can be divided into many different groups based on their characteristics and size, including viruses, bacteria, fungi, algae, and other microorganisms. Fungi include a vast number of species and play an important role in the Earth's ecological environment. They also serve useful purposes in the production of pharmaceuticals and fermented foods. However, fungi can also damage food, homes, and buildings, affecting not only their appearance but also indoor hygiene. Some fungi can cause infections or trigger allergic reactions.Microbial growth generally requires suitable nutrients, moisture, and favorable environmental conditions. Damp environments are particularly favorable for the growth of mold and other microorganisms. Microbial spores are commonly present in the air and can settle on surfaces. When sufficient moisture and other favorable conditions are present, mold can grow and reproduce.Effects on the Human Body: Damp environments are particularly prone to mold growth on food, building materials, and other surfaces. People living or working in damp buildings may be exposed to mold spores and other biological particles, which can irritate the respiratory system and trigger allergic reactions or worsen asthma symptoms. The health effects associated with microorganisms can generally be divided into three categories: infection, allergic reactions, and other effects caused by biological substances or toxins. The severity of these effects depends on the type and amount of exposure and the susceptibility of the individual.People with allergies or asthma, as well as those with weakened immune systems, may be particularly sensitive to mold and other biological contaminants. Keeping indoor spaces dry, repairing water leaks promptly, and removing [...]

High-Efficiency Particulate Air (HEPA) filtration can substantially reduce airborne particulate matter indoors. Research has also investigated whether reducing indoor particle exposure can produce measurable benefits to cardiovascular health.One study conducted in Denmark examined 21 nonsmoking couples between the ages of 60 and 75 in their homes. The randomized, double-blind crossover study exposed participants to particle-filtered air during one 48-hour period and nonfiltered air during another 48-hour period. The researchers measured indoor particulate concentrations and assessed several health indicators, with microvascular function as the primary outcome.The researchers found that filtration substantially reduced exposure to indoor particles. More importantly, microvascular function improved by 8.1% (95% confidence interval, 0.4%–16.3%) during the filtration period. Microvascular function was assessed by measuring changes in peripheral arterial tone following temporary restriction of blood flow to the arm.The findings are consistent with other research showing that exposure to particulate matter can affect vascular function and that reducing indoor particulate exposure may have measurable physiological benefits. However, this study was small and lasted only 48 hours. It measured a marker of vascular function rather than cardiovascular disease or cardiovascular events. In addition, the researchers did not find statistically significant changes in the secondary biomarkers of inflammation and oxidative stress after correcting for multiple comparisons. The results should therefore be viewed as evidence of a possible short-term cardiovascular benefit of reducing particle exposure, rather than proof that HEPA filtration prevents cardiovascular disease.Subsequent research has produced additional evidence that indoor air filtration can affect cardiovascular measures, although results have not been completely consistent across studies and [...]

Radon is a naturally occurring radioactive noble gas that is colorless, tasteless, and odorless.Radon enters indoor spaces primarily through cracks and openings in foundations, construction joints, gaps around pipes, and other openings in floors and walls that are in contact with the ground. As a result, radon levels can be higher in basements and other areas of a building that are close to the soil. However, any home can have elevated radon levels, whether it is new or old, well sealed or drafty, and whether or not it has a basement.The primary health risk associated with long-term exposure to high levels of radon is an increased risk of lung cancer. Research conducted in Europe, North America, and China has confirmed that residential radon exposure contributes to lung cancer. In Canada, radon exposure is estimated to account for approximately 16% of lung cancer deaths.Some households obtain their drinking water from groundwater sources such as springs and wells. Groundwater can contain radon when it passes through rocks and soil containing naturally occurring uranium and radium. Radon can be released from water into indoor air, particularly when water is used for showering and other household activities. However, soil gas is generally the more important source of radon in homes.There are several methods to reduce radon levels in the home, including sealing major entry routes and improving ventilation where appropriate. However, these measures may not be sufficient by themselves when radon levels are high. The most common and effective method for reducing radon in an existing home is an [...]

Research indicates that exposure to chlorinated swimming pools, particularly indoor pools, may irritate the respiratory system and can aggravate asthma in some people. Experts caution that swimmers should not overlook this potential factor while exercising.Chlorine is necessary to disinfect swimming-pool water and prevent the spread of disease-causing microorganisms. However, when chlorine reacts with sweat, urine, dirt, and other substances brought into the water by swimmers, it can form chemical irritants called chloramines. These compounds can accumulate in the air above indoor pools and may cause respiratory symptoms such as coughing and wheezing, particularly in people with asthma.Researchers have paid particular attention to this issue because swimming is often recommended as a form of exercise for people with asthma. The benefits of swimming should therefore be considered together with the quality of the pool water and surrounding air. Proper pool maintenance, adequate ventilation, and good swimmer hygiene can help reduce the formation and accumulation of chloramines.A strong chemical odor around a swimming pool does not necessarily mean that the pool contains too much chlorine. The familiar “chlorine smell” is often caused by chloramines rather than free chlorine itself. If swimmers notice a strong chemical odor or experience coughing, wheezing, eye irritation, or other respiratory symptoms, they should notify the pool operator.In some swimming facilities, odors may also come from other areas of the facility, so swimmers should consider the entire swimming environment rather than assuming that a strong smell automatically indicates excessive chlorine in the pool water.By Michael Chiu, MWS, CIPreviously published in Ming Pao Daily [...]

Through the media, residents often hear about Ontario's Air Quality Health Index (AQHI) and air-quality alerts issued by the Ontario government. Unlike the U.S. Air Quality Index (AQI), Ontario's AQHI is a health-based scale from 1 to 10+, calculated using concentrations of ground-level ozone, fine particulate matter (PM2.5), and nitrogen dioxide. The higher the number, the greater the potential health risk.Air pollution in Ontario comes from both local and long-distance sources. Pollution can travel across provincial and international borders, including from the United States, while weather conditions such as stagnant air can allow pollutants to accumulate. Wildfire smoke has also become an increasingly important source of fine particulate pollution in Ontario and across Canada.Ground-level ozone and particulate matter are important components of smog. Ground-level ozone forms when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in sunlight. It is different from the ozone layer in the stratosphere, which protects the Earth from harmful ultraviolet radiation. Particulate matter can come directly from sources such as vehicle exhaust, industrial activity, agriculture, construction, road dust, and wood burning, or it can form in the atmosphere through chemical reactions involving other pollutants.Air pollution remains an important health concern in Canada and throughout North America. Transportation, industrial activity, electricity generation, residential wood burning, agriculture, and wildfire smoke can all contribute to exposure to air pollutants. The relative importance of these sources varies considerably by location and season.Evidence shows that both short- and long-term exposure to air pollution can harm human health. Fine particulate matter is associated with cardiovascular and [...]

Since the 1970s, homes in North America have increasingly been designed with more energy-efficient and airtight windows, doors, insulation, and building envelopes. The advantage of this design is that it reduces the loss of heated or cooled air, thereby conserving energy. The downside is that tightly sealed homes can have poor indoor air quality if there is insufficient ventilation.Gases and particles suspended in the air are major factors contributing to poor indoor air quality. Common household sources include cooking fumes, paint, wooden furniture, household cleaning products, beauty products, humidifiers, and combustion from heating or cooking appliances. Dust, pollen, and other particles can also be brought indoors on the clothes and shoes of family members returning home. Without adequate ventilation, filtration, and source control, some indoor pollutants can accumulate and may contribute to irritation, allergies, or respiratory problems.By Michael Chiu, MWS, CIPreviously published in Ming Pao Daily News - Updated and Revised in 2026

The latest research confirms that air pollution can be harmful to human health and, at high or prolonged levels of exposure, can contribute to premature death. Air pollution comes from many sources, with particulate matter and ozone among the most important pollutants affecting human health. Vehicle exhaust, emissions from factories and power plants, and smoke from indoor and outdoor wood burning are important sources of particulate matter and other air pollutants.The higher the ozone levels, the greater the risk to human health. Ozone is an extremely reactive oxidizing gas that can irritate the respiratory system and aggravate existing respiratory conditions. Research has shown that ozone can cause breathing difficulties, coughing, and asthma attacks. Children, older adults, and people with asthma or other respiratory conditions can be particularly sensitive to ozone exposure.Airborne particulate matter can also have serious health effects, particularly when people are exposed to elevated levels over long periods. Fine particulate matter can penetrate deep into the lungs and is associated with cardiovascular and respiratory disease, lung cancer, and premature death. Particulate pollution can also aggravate asthma and other respiratory conditions.People should recognize the importance of reducing exposure to air pollution and protecting the environment. Early prevention and effective control of pollution are essential. For indoor air, reducing pollution at its source, providing adequate ventilation when appropriate, and using a suitable air purifier can also help reduce exposure to airborne particulate matter.By Michael Chiu, MWS, CIPreviously published in Ming Pao Daily News - Updated and Revised in 2026