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許多人購買並飲用瓶裝水後，為了方便起見，習慣性地重複使用裝過水的塑膠瓶——例如放在車內或戶外工作時攜帶飲用水。然而，這並非明智之舉。一般來說，聚對苯二甲酸乙二醇酯（PET）——一種用於某些塑膠瓶和容器的材料——在近期的研究和檢測中被發現含有潛在致癌物：二乙基羥胺（DEHA）。出於安全考慮，這些塑膠瓶或容器應僅使用一次。如果必須長期使用，一周是絕對的極限，並且不應盛裝熱水或食物。重複清洗塑膠瓶或容器會導致塑膠分解並釋放致癌物，這些致癌物會溶解在瓶內的水中，一旦被攝入，可能對身體造成不可逆轉的永久性損害。選擇水瓶時，應選擇可重複使用的塑膠瓶、玻璃瓶或不鏽鋼內膽的瓶子。每次使用後務必徹底清洗，以防止細菌在溫暖潮濕的瓶身中滋生。消費者在購買水瓶時，應基於邏輯和科學做出理性選擇，避免盲目相信廣告中關於健康、安全或「神奇」設計的誇大宣傳。作者：Michael Chiu，MWS，CI。本文曾發表於《明報》，並於2026年更新修訂。

腹瀉仍然是全球主要的公共衛生議題之一。世界衛生組織估計，每年約有17億兒童發生腹瀉病例，約有443,832名五歲以下兒童死於腹瀉。腹瀉在低收入和中等收入國家尤其嚴重，這些國家獲得安全飲用水、衛生設施和個人衛生條件仍面臨挑戰。不安全的飲用水是腹瀉的重要來源。 2022年，全球至少有17億人飲用糞便污染的水源。飲用水的微生物污染可傳播包括腹瀉、霍亂、痢疾、傷寒和小兒麻痺在內的多種疾病。改善安全飲用水、充足的衛生設施和良好的個人衛生習慣可以顯著降低腹瀉的風險。重要的預防措施包括使用安全飲用水、用肥皂洗手、保持良好的食品衛生以及使用適當的衛生設施。家庭用水處理也是一項重要的公共衛生幹預措施，尤其對於那些依賴受污染或不可靠供水的人。處理方法包括過濾、煮沸、氯化以及其他旨在減少微生物污染的技術。世界衛生組織持續評估家庭用水處理技術去除或滅活病原體的能力。因此，安全飲用水不僅僅是口感或便利的問題。在飲用水受到污染或不可靠的情況下，提高飲用水安全在預防疾病方面發揮重要作用，尤其是在幼兒族群中。作者：Michael Chiu，MWS，CI。本文原刊於《明報》，並於2026年更新修訂。

天氣變化或季節更替時，許多人會出現流鼻水、鼻塞、眼睛發癢和喉嚨痛等症狀。他們往往以為自己只是感冒了，而忽略了這些症狀可能是過敏反應的可能性。過敏和感冒的症狀可能相似，但區分二者有助於人們選擇合適的治療方法。過敏症狀包括：流鼻水（通常伴隨稀薄清澈的鼻涕）、打噴嚏、鼻塞、喘息、眼睛、鼻子或喉嚨發癢。過敏症狀也可能包括流淚，但通常不會引起發燒。原因/持續時間：這些症狀通常是由接觸過敏原引起的，例如花粉、塵蟎、黴菌、動物皮屑以及某些化學物質或其他物質。只要持續接觸過敏原，症狀就會持續存在。季節性過敏在花粉濃度高的時期特別常見。病毒引起的普通感冒症狀包括：流鼻水或鼻塞、打噴嚏、喉嚨痛、咳嗽、輕微發燒、頭痛、疲倦或虛弱感。感冒期間鼻涕可能會變稠或顏色改變，但僅憑鼻涕的顏色無法可靠地區分感冒和過敏。病因/持續時間：感冒症狀通常在接觸呼吸道病毒後1-3天出現，並在7-10天內好轉，但咳嗽或其他症狀可能會持續更長時間。如果症狀嚴重、持續存在、反覆幹擾日常生活或出現明顯的呼吸困難，則應就醫。作者：Michael Chiu，MWS，CI。先前發表於《明報》—已更新修訂 [...]

在考慮購買空氣淨化系統時，消費者應了解各種可用的技術、每種技術可以去除的污染物種類以及系統的限制。選擇合適的空氣清淨機應根據特定的室內空氣問題、房間大小、有效淨化空氣量以及製造商的維護要求而定。沒有任何一種空氣淨化技術可以去除所有類型的室內污染物。有些空氣清淨機採用電離或其他技術使顆粒帶電。這些設備可以使空氣中的顆粒帶電，並吸附在物體表面或被收集系統捕獲。然而，一些產生離子的空氣清淨機也會產生臭氧作為副產品。臭氧本身就是一種空氣污染物，會刺激肺部並加重呼吸道症狀。因此，消費者應謹慎選擇那些有意產生臭氧或會產生大量臭氧作為副產品的空氣清淨機。美國環保署不建議在有人居住的空間內使用臭氧產生器來控制室內空氣污染。此外，電離技術也不應與普通的機械過濾混淆。電離器可能會導致顆粒物沉積在牆壁、地板、家具和其他表面上，而不是真正將其從室內環境中去除。不同產品的性能差異很大，因此對於聲稱空氣清淨機「殺菌」或「淨化空氣」的說法應謹慎評估。機械過濾是去除空氣中粒狀物的較成熟的方法之一。高效能空氣微粒過濾器（HEPA）旨在高效去除氣流中的極小顆粒。 [...]

人體含有大量水分，水是維持正常身體功能的必需物質。水有助於調節體溫、輸送營養物質、排出廢物，並維持器官和組織的正常運作。因此，攝取充足的水分對保持健康至關重要。飲水小撇步：全天定時飲水。並沒有規定每個人必須每天喝八杯（每杯8盎司）水。每個人所需的水分量因年齡、體型、飲食、活動量、氣候和其他因素而異。運動或在炎熱天氣中活動的人通常需要補充更多水分。不要等到極度口渴才喝水，尤其是在運動或炎熱天氣下。口渴是身體需要補充水分的重要訊號，但在劇烈運動或高溫環境下，體液流失會迅速發生。全天多喝水。帶一個水瓶去上班或上學，隨時準備水，提醒自己定時飲水。水是補充水分的絕佳選擇。酒精會增加體液流失，尤其是在大量飲酒的情況下。正常量的含咖啡因飲料通常仍有助於每日液體攝入，不會自動導致脫水。運動時應飲用足夠的水以補充因出汗而流失的水分，尤其是在長時間或劇烈運動以及炎熱天氣下。長時間高強度運動期間，可能還需要補充電解質。全天飲用足夠的水分，並根據自身需求調整飲水量。一般情況下，無需大量飲水 [...]

Many people wonder whether they should clean their home's air ducts every year. The answer varies from home to home.Air duct cleaning companies, from a business perspective, may recommend regular cleaning to prevent or alleviate allergies or asthma. In reality, there are many factors that contribute to poor indoor air quality and related health problems. While air duct cleaning may sometimes be helpful, it is not generally considered a comprehensive solution for improving indoor air quality.The U.S. Environmental Protection Agency (EPA) does not recommend routine cleaning of air ducts. Cleaning may be appropriate when there is substantial visible mold growth inside hard-surface ducts, when the ducts are infested with insects or rodents, or when substantial amounts of dust and debris have accumulated and are actually being released into the home. The EPA notes that there is currently no evidence that simply having dirty air ducts increases the amount of dust in a home or that duct cleaning prevents health problems.Residents may have difficulty determining the condition of their ductwork because much of the system is inaccessible. However, ordinary household dust should not be assumed to be accumulating in ducts in quantities that make duct cleaning necessary. Dust mites and their waste can contribute to allergies and asthma, but they primarily live in household furnishings such as bedding, carpets, and upholstered furniture rather than inside air ducts.Many people mistakenly believe that indoor dust is routinely distributed throughout the home by the air ducts. In reality, dust enters and accumulates in homes from many sources, including outdoor [...]

Caffeine is a central nervous system stimulant that can temporarily reduce drowsiness and increase alertness. Caffeine-containing products such as coffee, tea, soft drinks, chocolate, and energy drinks are extremely popular, making caffeine one of the most widely consumed psychoactive substances in the world.Coffee and tea are two of the most common natural sources of caffeine, although the amount varies considerably depending on the type of product and how it is prepared. Caffeine is also found naturally in ingredients such as cocoa, guarana, and yerba mate. Energy drinks and other foods may also contain added caffeine.Unlike some other central nervous system stimulants, the effects of caffeine are temporary. For most people, moderate caffeine consumption can increase alertness and attention. However, sensitivity varies from person to person, and consuming caffeine later in the day can interfere with sleep.Regular caffeine consumption can cause the body to become accustomed to caffeine. If someone who regularly consumes caffeine suddenly stops, withdrawal symptoms such as headache, fatigue, irritability, and difficulty concentrating may occur. These symptoms are generally temporary, and gradually reducing caffeine intake can make withdrawal easier.Research has found an association between caffeine consumption and a lower risk of developing Parkinson's disease in some populations. However, this does not establish that caffeine prevents Parkinson's disease, and more research is needed to understand the relationship.Excessive caffeine intake can cause symptoms such as nervousness, irritability, anxiety, insomnia, headache, increased heart rate, heart palpitations, and stomach upset. Health Canada recommends a maximum daily caffeine intake of 400 milligrams for adults 18 and older. The [...]

Laser printers and photocopiers can release small amounts of pollutants into indoor air during operation. Older laser printers, in particular, could produce ozone during the printing process. Therefore, it is better not to place a printer immediately beside a person's desk, especially in a poorly ventilated room.Laser printers have become common in homes and offices. During printing, toner is transferred to the paper and then fixed to the paper by heat and pressure. The printing process can release particles and volatile organic compounds (VOCs), while some older laser-printer technologies could also generate ozone.Ozone is a respiratory irritant, and exposure to elevated concentrations can cause coughing, throat irritation, breathing difficulties, and other respiratory effects. However, the amount of ozone produced varies considerably between printer models. Studies by the National Institute for Occupational Safety and Health (NIOSH) found that older printers using corona-wire technology could produce significantly more ozone, while newer printers using charged-roller technology produced very little ozone.Laser printers and copiers can also contribute to indoor particulate matter and VOCs. The U.S. Environmental Protection Agency (EPA) recommends good ventilation when operating printers and copiers and notes that increased filtration and ventilation can reduce exposure to indoor particles from these devices.For better indoor air quality, place printers and copiers in well-ventilated areas rather than directly beside people who spend many hours at a desk. Regular maintenance should also be performed according to the manufacturer's instructions. If a printer produces a strong or unusual odor, excessive dust, or other noticeable emissions, improving ventilation and having the equipment inspected [...]

A parasite is an organism that lives in or on another organism, known as a host, and obtains nutrients or other benefits from the host. Parasitic organisms can cause harm to their hosts, although the effects vary depending on the type of parasite and the host.Parasites that infect humans can enter the body through contaminated food or water, insect bites, contact with contaminated soil or surfaces, or direct contact with an infected person or animal. Some parasites can live in the intestines, while others can infect tissues, blood, or other parts of the body.However, it is impossible for humans to completely isolate themselves from parasites. According to the World Health Organization, parasitic infections remain an important global health problem, particularly in tropical and subtropical regions where inadequate sanitation, unsafe water, poor hygiene, and limited access to health care can increase the risk of infection. Diseases such as lymphatic filariasis, schistosomiasis, and soil-transmitted worm infections affect millions of people worldwide.Parasites can cause a wide range of health problems, including abdominal pain, diarrhea, anemia, malnutrition, fever, and damage to organs or tissues. Lymphatic filariasis, for example, is caused by microscopic parasitic worms transmitted through mosquito bites and can lead to severe swelling and enlargement of affected parts of the body.There may also be a beneficial side to the study of parasites. Researchers have investigated whether certain parasitic worms, known as helminths, or substances produced by them could help regulate an overactive immune system. This research has led to studies involving conditions such as inflammatory bowel disease and [...]

Air conditioning, commonly abbreviated as “AC,” is a system or appliance that removes heat from an indoor space, typically through a refrigeration cycle, and transfers that heat outdoors. Modern air-conditioning systems can also dehumidify and filter indoor air. When heating, ventilation, and air conditioning are considered together, the overall system is commonly referred to as HVAC (heating, ventilation, and air conditioning).Air conditioning has become increasingly widespread around the world, particularly in regions with hot or humid climates. In East Asia, it is now common in countries and regions including Japan, South Korea, mainland China, Hong Kong, and Taiwan. China has experienced especially rapid growth in air-conditioning ownership and cooling demand. The International Energy Agency (IEA) estimates that nearly 90% of households in Japan and the United States have an air conditioner, while air-conditioning ownership in China has risen substantially over the past decade.Residential systems in East Asia commonly include room air conditioners, ductless mini-split systems, and multi-split systems. These systems can provide efficient cooling to individual rooms or several rooms without requiring the large duct networks used by many North American central-air systems. As incomes, access to electricity, and demand for thermal comfort have increased, air conditioning has also expanded in Southeast Asia. Nevertheless, ownership remains considerably lower there than in countries such as Japan and the United States, despite the region's substantial need for cooling. The IEA projects continued rapid growth in residential air-conditioning use in Southeast Asia. In the United States, air conditioning is now widespread across most regions rather than being concentrated [...]