Knowledge Center

Dry indoor air can cause or worsen symptoms such as dry skin, irritated eyes, a dry throat, and irritation of the nasal passages. These problems are particularly common during winter in cold climates because heating indoor air lowers its relative humidity. Low humidity can also contribute to static electricity and the drying or cracking of some wood products and building materials.Many households use humidifiers to increase indoor humidity. However, adding moisture to indoor air must be done carefully. The U.S. Environmental Protection Agency (EPA) generally recommends maintaining indoor relative humidity between 30% and 50%. Keeping humidity within this range can help avoid both excessively dry conditions and the excessive moisture that encourages mold and other biological growth.Excessive humidity can create its own indoor-air-quality problems. Condensation on windows and other cold surfaces can provide moisture for mold growth, while persistently damp conditions can encourage dust mites and other biological contaminants. Mold and dust mites can aggravate allergy and asthma symptoms in susceptible individuals.Different types of humidifiers work in different ways. Common residential types include ultrasonic humidifiers, impeller or cool-mist humidifiers, evaporative humidifiers, and steam vaporizers. Their effects on indoor air quality can differ significantly.Ultrasonic and impeller humidifiers can disperse minerals present in tap water into the air along with the water droplets. Depending on the water supply and the device, this can produce a visible mineral dust and increase concentrations of particulate matter indoors. These devices can also disperse microorganisms if the water reservoir is contaminated. The EPA recommends using low-mineral or distilled water in ultrasonic [...]

In the past, reverse osmosis (RO) water filtration technology was used primarily in specialized applications, including military and space technology. Today, RO is widely used for drinking-water treatment in homes, businesses, and other settings. The technology is particularly useful for reducing certain dissolved contaminants that are difficult to remove with conventional filtration.In response to consumer demand for treated drinking water, many households and bottled-water producers use RO or other advanced water-treatment technologies. However, not all bottled-water products use RO, and the treatment process varies by brand and product.The most important component of an RO system is a semipermeable membrane. Under pressure, water passes through the membrane while many dissolved substances and microorganisms are rejected. Depending on the membrane and system design, RO can substantially reduce contaminants such as lead, copper, chromium, arsenic, fluoride, nitrate, and some microorganisms. RO can also reduce substances responsible for certain tastes and odors. However, the effectiveness of an RO system depends on the specific membrane, water quality, operating conditions, and maintenance. Reverse osmosis does not simply produce “pure” water. It removes many contaminants but can also remove minerals that are naturally present in drinking water, and it does not necessarily remove every contaminant. RO systems also produce a reject-water stream containing the concentrated contaminants removed from the treated water.Many household RO systems combine the membrane with other treatment stages, such as activated-carbon filters. Activated carbon can reduce chlorine, tastes, odors, and certain organic compounds, while the RO membrane provides additional treatment of dissolved contaminants. Both the membrane and pre- and [...]

Through various sources such as dust, paint, soil, water, or food—prolonged accumulation or short-term excessive exposure, contact, ingestion, or consumption of lead-containing substances can lead to lead poisoning. The human body does not naturally contain lead. Lead is a harmful inorganic heavy metal that can damage any organ in the body, with the greatest impact on children and pregnant women. The dangers of lead poisoning are becoming increasingly recognized. If children absorb excessive amounts of lead, it can lead to symptoms such as slow learning, hyperactivity, hearing loss, mental retardation, loss of appetite, and developmental delays. Pregnant women may experience side effects such as miscarriages, infertility, or mental retardation in their infants. For adults, lead poisoning can also cause high blood pressure, anemia, kidney failure, memory loss, and damage to the nervous and digestive systems. In severe cases, it can be fatal.Lead can contaminate drinking water by leaching from municipal water pipes, indoor plumbing, and faucets; even lead-free copper pipes may have been soldered with lead. According to reports, most interior walls in buildings constructed before 1978 were painted with lead-based paint. Certain medications, vitamins, and food or juice cans may also contain lead.The symptoms of lead poisoning are not obvious and may be mistaken for other illnesses. As lead poisoning becomes more severe, patients may experience a loss of appetite, fatigue, headaches, tooth decay, insomnia, and memory loss, among several other problems.Surgery cannot remove lead from the body. To prevent lead poisoning, one should avoid and eliminate sources of lead, maintain a balanced diet [...]

To prevent harmful bacteria and microorganisms from contaminating drinking water and water distribution systems, most municipal water supplies use disinfectants such as chlorine or chloramine to inactivate disease-causing microorganisms. Disinfection is an important part of maintaining safe drinking water. However, chlorine and other disinfectants can react with naturally occurring organic matter in water and form disinfection by-products (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs).Some DBPs have been associated with potential health effects. Long-term exposure to certain DBPs, particularly at higher concentrations, has been studied in relation to cancer and other health outcomes. However, the evidence varies among individual compounds and studies, and the presence of chlorine in drinking water does not mean that the water is unsafe. Municipal water systems monitor and control disinfectant levels and DBPs to maintain effective disinfection while limiting these by-products. Chlorinated water can also release small amounts of volatile disinfection by-products into indoor air, particularly during activities such as showering and bathing. People can therefore be exposed through both drinking water and inhalation. Some compounds can also be absorbed through the skin. However, the relative importance of these exposure routes varies according to the particular chemical, water concentration, temperature, duration of exposure, and individual circumstances. Claims that a ten-minute shower exposes the body to the equivalent of drinking eight glasses of water are not supported as a general scientific measure of exposure.The most important consideration is therefore the quality of the local drinking-water supply. Consumers who are concerned about chlorine or specific contaminants should first consult their municipality's drinking-water-quality [...]

Due to geographical conditions and local geology, many municipal water supplies and private wells in North America contain significant amounts of calcium and magnesium and are therefore considered hard water. Hard water is generally safe for outdoor and indoor uses, but for household activities such as showering, washing dishes and clothes, and operating water-using appliances, soft water can provide practical benefits by reducing scale and improving soap and detergent performance.The drawbacks of hard water include the need for more soap or detergent when washing; soap scum on bathroom surfaces, which can be difficult to clean; mineral deposits and spots on cups, dishes, faucets, and other surfaces; and scale buildup in water heaters and other appliances. Scale can reduce the efficiency of water-heating equipment and, over time, contribute to maintenance problems and reduced equipment life. Hard water can also leave mineral deposits and soap residue on the skin and hair, which some people may find unpleasant or drying.The minerals primarily responsible for water hardness are dissolved calcium and magnesium. Hardness is commonly expressed as grains per gallon (GPG) or milligrams per litre (mg/L) as calcium carbonate. According to the Water Quality Association, water with less than 1 GPG is generally considered soft, while water above 7 GPG is considered hard.Water Hardness Standards:Soft water – Less than 1 GPGSlightly hard water – 1–3.5 GPGModerately hard water – 3.5–7 GPGHard water – 7–10.5 GPGVery hard water – Over 10.5 GPGWater hardness in Ontario varies considerably depending on the local geology and water source. Municipal water supplies in different [...]