Biological Pollution Endangers Children
1. What are the types of biological pollution?
Biological pollution can be divided into four categories: First, mold, which is the main cause of allergic diseases; second, pollen from plants; third, bacteria and viruses carried by human bodies, animals, soil, and plant debris; fourth, dust mites, as well as hair and dander shed from cats, dogs, and birds.
2. What are the types of indoor biological pollution?
Although air is not a natural environment for the generation and growth of microorganisms—due to the lack of sufficient moisture and nutrients necessary for bacterial growth—humans, as higher organisms, are an important source of contamination. Gases expelled during human metabolism and unpleasant odors emanating from skin, organs, and unclean clothing become sources of hetero-odor pollution. Prolonged exposure to such environments adversely stimulates the cerebral cortex, leading to nausea, dizziness, fatigue, and loss of appetite. Human activities introduce certain microorganisms, including pathogens, into the air, facilitating disease transmission. Indoor air, especially in poorly ventilated and crowded spaces, harbors more microorganisms. In addition to existing atmospheric microorganisms (non-pathogenic saprophytic microorganisms, Bacillus species, Achromobacter species, Micrococcus species, some actinomycetes, yeasts, and fungi), there may also be pathogenic microorganisms originating from humans (such as Mycobacterium tuberculosis, Corynebacterium diphtheriae, hemolytic streptococci, Staphylococcus aureus, Neisseria meningitidis, cold viruses, measles viruses, etc.), which could potentially spread airborne diseases. Generally, the total number of bacteria in indoor air far exceeds that in outdoor air, with significant variations depending on building usage and population density. Some indoor ornamental plants produce fibers, pollen, and spores that can trigger asthma and rashes in sensitive individuals. Pets kept indoors release dander, as well as bacteria, viruses, fungi, spores, and mold into the air, acting as disease vectors. Moreover, air conditioners, storing water at suitable temperatures, can become breeding grounds for certain bacteria, molds, and viruses. Studies show that bacteria and fungi in air conditioners can exacerbate or induce respiratory allergies, causing asthma.
3. How is the indoor bacterial index determined?
Research indicates that after 80 minutes of crowd gathering indoors, the total bacterial count in the air reaches 4300 cfu/m³ (impact method) and 44 cfu/m³ (settling method). In rooms with compound pollution, within just 20 minutes, the total bacterial count in indoor air reaches 4000 cfu/m³ and 33 cfu/m³, with CO2 concentration reaching 0.08%. At this point, a minority of sensitive individuals begin to experience odor discomfort at a rate of 24.1%. When the bacterial count reaches 6000 cfu/m³ and 75 cfu/m³, and CO2 concentration reaches 0.15%, the rate of discomfort due to odors rises to 55% among the population.
The Soviet Union proposed reference standards for evaluating bacterial hygiene in indoor air: winter < 4500 cfu/m³, summer < 1500 cfu/m³. Japanese data on the relationship between colony counts and air cleanliness suggests that air with less than 30 cfu/m³ is clean, while air with less than 75 cfu/m³ is ordinary.
Based on these data, combined with current urban per capita floor space in China, the national standard specifies that the total bacterial count in indoor air should be ≤4300 cfu/m³ using the impact method and ≤45 cfu/m³ using the settling method.
4. Do you know how atmospheric microbial pollution severely affects citizens' health?
The latest monitoring study provided by the School of Public Health at Shanghai Medical University shows that atmospheric microbial pollution is affecting citizens' health.
1) Residents near a garbage transfer station in the southern district
Monitoring results show that among six sampling points, the area around the garbage transfer station at No. 43 Lin Road has the highest number of pathogenic bacteria, largely due to its release of large amounts of bacteria into the surrounding atmosphere. During dusk, the garbage transfer station is in a "gap" period after its busy operations. There is no garbage exposed inside or outside the station. However, passing by the entrance of the garbage transfer station, one can smell an odor. The cement ground is black and damp. Building No. 5 at Lane 43, where residents live next to this garbage transfer station, faces it directly across a narrow alley only 3 meters wide. Resident Mr. Wu reports that the garbage transfer station brings many flies, mosquitoes, cockroaches, and other small unidentified flying insects. Especially in the morning, over ten garbage trucks line up at the entrance of the transfer station to dump garbage. Throughout the year, Mr. Wu's family almost never opens their windows. Mr. Wu, aged 37, works in an office. As soon as he gets home, he feels his nose is blocked and experiences dry coughs. His father suffers from emphysema, and his 67-year-old mother, retired at home due to poor mobility, rarely goes out. "Shortness of breath, difficulty breathing." Her throat pain worsens day by day.
2) Children living in commercial bustling areas
Investigations found that the degree of atmospheric microbial pollution in the Nanjing Road area is significantly higher than in the Xinzhuang area. Compared to adults, children are more sensitive to air pollution. Epidemiological surveys conducted by faculty and students of Shanghai Medical University on children in these two areas revealed that the incidence rates of nasal congestion, allergic asthma, and upper respiratory infections, as well as overall disease prevalence, were significantly higher among students at the No. 1 Primary School on Nanjing West Road compared to those at the Xinzhuang Town Primary School. Physical examination results of children from both schools showed that the risk of children at the No. 1 Primary School on Nanjing Road suffering from pus accumulation in the nasal passages, allergic rhinitis, pharyngeal congestion, and tonsillitis was 1.57 to 6.50 times higher than that of children at the Xinzhuang Town Primary School. Students at the No. 1 Primary School on Nanjing West Road generally had lower lung capacity indices compared to students at the Xinzhuang Town Primary School.
Xiao Shi is a fifth-grade student at the No. 1 Primary School on Nanjing West Road. His family rents a room on the fifth floor of the school's teaching building. Xiao Shi, 12 years old, lives with his parents and younger brother. No one in the family smokes, and neither parent has chronic respiratory diseases or asthma history. However, on the "Student Health Survey Form," the parents filled in "chronic pharyngitis" and "chronic rhinitis" for Xiao Shi. He coughs incessantly, especially at night, his mother, Ms. Gu, added. After visiting multiple hospitals, doctors couldn't find any clear diagnosis. Later, they took him to see an expert at Huashan Hospital, who said it was a "habitual illness." They tried taking Chinese medicine for half a month but saw no effect. The parents then bought Xiao Shi Sophora root lozenges and watermelon frost, which he consumed continuously. Their windows face east towards an elevated road and west towards Nanjing West Road. "After opening the windows, a thick layer of dust accumulates on the table. Sunlight shines through the glass window, and dust dances proudly in the light." Xiao Shi habitually pinches his nose. His classroom is on the fourth floor. Even if the classroom floor is cleaned and a window left open overnight for ventilation, the air in the classroom still smells pungent in the morning. By the next morning, the floor is covered with dust. Feeling mentally foggy, Xiao Shi rests his head on the table when the teacher isn't around. Or he takes out his water bottle to drink some water and soothe his throat. On their windowsill, Xiao Shi planted a pot of grass and a pot of vegetables. He says greenery purifies the air. When his throat feels uncomfortable, he smells them.
3) Residents neighboring open-air markets
Currently, Shanghai still has a certain number of "street markets" that not only occupy roads but also cause air microbial pollution. The street market on Yongnian Road has been operating for nearly ten years, and residents along both sides of the market have been hoping for its relocation indoors. Mrs. Zhou, who lives on the second floor of No. 55, mentions that the smell of chickens and ducks being slaughtered at nearby stalls often lingers in the air, and garbage piles up here and there in the market. Some vendors even use the public water pool as a urinal. Mrs. Zhou suffers from chronic bronchitis. While working as a nursery attendant at a daycare center on Xujiayuan Road, her health was always good. However, after retirement, staying at home longer led to frequent colds and coughs. Despite blocking the north-facing window overlooking the market with curtains and burning rose incense daily, nothing seemed to help. Residents along both sides of Yongnian Road market and those in the Xinhua community use liquefied gas or gas as fuel, and their housing structures are old-style lanes. However, the total bacterial count and fungal numbers measured in the surrounding air of the former group are five and four times higher, respectively, than those of the latter group. Surveys indicate that the former group has significantly higher rates of colds, acute and chronic respiratory diseases, and infectious diseases compared to the latter group. The air pollution around the Yongnian Road market is severe. Professor Song from the School of Public Health at Shanghai Medical University, who participated in the monitoring, analyzed that besides the dense population and frequent foot traffic, meat, poultry, eggs, and vegetables carry various microorganisms on their surfaces. Additionally, poor hygiene awareness among vendors, chaotic market management, and untimely cleaning of garbage and sewage all contribute to air microbial pollution.
4) Residents near botanical gardens say "fresh air"
Research results show that forests, shrubs, and lawns have obvious purification effects on air microbes. Experts urge that enhancing greening can reduce air microbial pollution. Comprehensive survey interviews reveal that almost every surveyed site affected by atmospheric microbial pollution received low evaluations regarding nearby greenery, and everyone hopes for more greenery around them.
Residents of the Longwu Road No. 1137 Lane new village near the Shanghai Botanical Garden all responded that the air near the botanical garden is very fresh. Ms. Chen, aged 61, told reporters that the air in the new village is good, the wind blows refreshingly, and she and several elderly neighbors do not suffer from coughing or other respiratory diseases, maintaining good health.
5. Why can plants serve as environmental pollution monitors?
Scientists have observed that plants exhibit varying resistances to different harmful gases. Some plants are highly sensitive to harmful gases and are affected at very low concentrations, while others remain unaffected or only slightly affected at higher concentrations. For example, cattails are most sensitive to fluorides, showing symptoms of damage when fluoride concentrations accumulate to 3×10^-5～4×10^-5. Pine trees, apricot trees, and plum trees show symptoms at 5×10^-5～2×10^-4, while resistant cotton shows no damage even at 5×10^-4. Interestingly, different plants have different sensitivities to fluorides at different times. Apricot trees are most sensitive at 10 a.m., while Metasequoia glyptostroboides are most sensitive at 2 p.m. From April to May each year, all plants' resistance to fluoride pollution drops sharply.
People can utilize the sensitivity of plants to monitor atmospheric pollution. Now people have identified various "alarm plants" for monitoring atmospheric pollutants. For instance, purple clover, carrots, and spinach can monitor sulfur dioxide pollution, while cattails, Polygonum chinense, Fagopyrum dibotrys, apricots, plums, and grapes can monitor fluoride pollution. Apples, corn, peaches, and onions can monitor chlorine pollution. Plants react to atmospheric pollution much more sensitively than humans and animals. When the concentration of harmful gases in the air is only a few parts per million, plants start "raising alarms," warning people to take action early to eliminate pollution.
Using plants as alarms is simple and convenient, monitoring pollution while beautifying the environment, achieving two goals at once.
6. Why does the city advocate planting lawns?
Lawns give people a sense of freshness, coolness, and pleasure, providing a pleasant, clean, and safe working and living environment. Green grass acts like a vacuum cleaner, purifying the air and filtering out dust, reducing dust and thus decreasing the bacterial content in the air. According to measurements, the Nanjing train station has a high amount of dust, with 49,100 bacteria per cubic meter of air, while above the large lawn at the Nanjing Zhongshan Botanical Garden, there are only 688 bacteria per cubic meter.
Lawns are also the best consumers of carbon dioxide. A well-growing lawn absorbs 1.5 grams of carbon dioxide per square meter per hour. A person exhales about 38 grams of carbon dioxide per hour, so having a 25-square-meter lawn can absorb all the carbon dioxide exhaled by one person. It is evident how important lawns are in cities for purifying the air, which is why people feel the air is particularly fresh on large lawns.
Lawns can also reduce noise. A 20-meter-wide lawn can reduce noise by about 2 decibels. A 250-square-meter lawn in Hangzhou's botanical garden, when compared to a stone slab road of the same area, reduces sound levels by 10 decibels. Lawns can also regulate temperature and humidity. In summer in Nanjing, the surface temperature of bare soil can reach 40°C, asphalt roads 55°C, while the surface temperature of lawns is only 32°C. Laying more lawns can reduce surface heat emission and lower urban temperatures. Measurements show that lawns can lower temperatures by 3～3.5°C in summer and increase them by 6～6.5°C in winter. Simultaneously, lawns can increase air humidity by evaporating water absorbed from the soil into the atmosphere.
Grass varieties used for lawns can be divided into two major categories based on their adaptability to the environment: cool-season grasses and warm-season grasses. Cool-season grasses include creeping bentgrass, fine fescue, Kentucky bluegrass, and perennial ryegrass, which can withstand cold and are suitable for northern China. Warm-season grasses include Zoysia japonica, centipedegrass, carpetgrass, and Bermuda grass, which are suitable for high-temperature regions and commonly used in southern China. Choosing grass varieties suited to local conditions is key to the success or failure of laying lawns.
Lush green lawns provide comfortable and tranquil green spaces, bringing civilization and beautiful environments to cities. Protecting high-quality lawns in cities is not as simple and easy as people imagine. Every step, from land preparation, soil improvement, seeding, to mowing, watering, fertilizing, pest control, etc., is crucial and quite costly. It is said that the United States spends as high as $4 billion annually on lawn maintenance.
7. What are the common causes of indoor air pollution in children's rooms?
1) Toxic and harmful gases produced by indoor construction and decoration, such as formaldehyde, benzene, ammonia, etc.;
2) Decorations and furnishings in children's rooms, such as carpets, bedspreads, and various decorations;
3) Pollution caused by children's toys, such as dust mite pollution in plush toys, paint pollution on wooden toys, and volatile substances in plastic toys;
4) Keeping pets like cats and dogs at home, with whom children like to play and spend time together, easily causing biological pollution such as bacteria, fungi, and viruses;
5) In kindergartens and schools, classrooms with too many children densely packed, making it easier for indoor air pollution to worsen.
8. What are the national regulations regarding indoor environmental indicators in children's rooms?
1) Carbon dioxide less than 0.1%. Carbon dioxide is a comprehensive indirect indicator of indoor air quality. If the concentration increases, it can make children feel nauseous and have headaches;
2) Carbon monoxide less than 5 mg/cubic meter. Carbon monoxide is the most common toxic gas in indoor air, easily damaging children's nerve cells and being extremely harmful to children's growth;
3) Total bacterial count less than 10 per dish. Children are in the stage of growth and development, with low immunity, so it is necessary to disinfect and sterilize the room;
4) Temperature. Children have poor body temperature regulation ability. In summer, the temperature should be controlled below 28℃, and in winter, the indoor temperature should be above 18℃. However, attention should be paid to the impact of air conditioning on children's health and reasonable use;
5) Relative humidity should be maintained between 30-70%. Low humidity can easily harm children's respiratory tract, while high humidity is unfavorable for sweat evaporation, causing discomfort to children;
6) Under the premise of ensuring ventilation, airflow should not exceed 0.3 m/s. Excessive airflow can make children feel cold;
7) Lighting. When children write, the light in the room should be evenly distributed without strong glare. Desk illumination should be no less than 100 lx;
8) Noise has a great impact on children's mental activities. It distracts children during learning activities, and prolonged exposure to noise can cause psychological stress, affecting physical and mental health. Noise in children's rooms should be controlled below 50 decibels.
9. How to prevent children from being affected by unhealthy indoor air?
How to prevent children from being affected by unhealthy indoor air? Experts from the Indoor Environment Testing Center suggest the following: strengthen ventilation in children's rooms. According to tests by indoor environment experts, children need about 15 cubic meters of fresh air per hour. In general households, children's rooms tend to be smaller. In kindergartens and schools, children are relatively concentrated, making it easy for air pollution to occur. If each child occupies 5 cubic meters of classroom space, the room needs to be ventilated three times per hour. Moreover, children's activities, playing, and movements easily aggravate indoor air pollution. Experts simultaneously suggest:
1) When outdoor air quality is good, lead children to participate in more outdoor activities;
2) During indoor activities and learning, if conditions allow, frequently open windows for ventilation, but prevent pollution intrusion and cold drafts harming children;
3) General families and kindergartens, schools should ideally be equipped with indoor air purifiers, allowing our next generation the right to breathe fresh air, which is a more important issue than taking care of children's clothing, food, shelter, and