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Tuesday, January 02, 2018, 14:41
Living in the heat of the moment
By Honey Tsang
Tuesday, January 02, 2018, 14:41 By Honey Tsang

The influence of climate change on the environment is never far from the news but less widely discussed are its effects on human health. Honey Tsang takes a stethoscope to the growing body of evidence that global warming harms our health

(INFOGRAPHIC: HONEY TSANG, MOK KWOK-CHEONG / CHINA DAILY)

It was the flu that made Jordan Lee Kin-fung, 10, miss an important final-term exam. The night before Nov 13 was a nightmare. Lee’s temperature hit 40 C and stayed there. He was admitted to Caritas Medical Centre and remained overnight until the fever went down.  

The boy was always sick. His mother, Ms Tao, noticed it started after she and her son moved into a cramped, unventilated subdivided flat in Sham Shui Po five years ago. Lee has suffered from poor health ever since. He’s been sick more times than he can count on the fingers of both hands.

The hot summer is the season mother and son fear the most. They suffered through the heat of summer for years, before caving in and turning on the air-conditioning, a luxury that shot their expenses through the ceiling. They hoped that the expense would keep Lee healthy.

A study by Emily Chan Ying-yang of the Chinese University of Hong Kong revealed that when the ambient temperature rose above 28.5 C, for children aged under 15 in Hong Kong the risk of being hospitalized for respiratory diseases rose by an average 19.5 percent for each increase in temperature of 1 C. That compared to a lower susceptibility of only 8.2 percent among the maturer group aged 15-59.

Chan is a pioneer in the field, and the first to assess the casualties wrought by warming temperatures in Hong Kong. When she examined the city’s hospitalization data between 1998 and 2006, she made a startling connection between daily mean temperature and lethality: Once the daily mean temperature increased 1 C above 28.2 C, the overall mortality rate increased 1.8 percent on the same day, and it increased exponentially. Thus for 30.2 C, 2 C above 28.2 C, the mortality rate would increase by 1.8 percent to the power 2. At 31.2 C, 3 C higher than the threshold, the mortality rate heightened by 1.8 percent to the power 3.

“It’s proved that every increase of 1 C above 28.2 C can be perilous to human health,” said Chan, professor of the Jockey Club School of Public Health and Primary Care at the CUHK. Chan has been shocked by the findings. 

Of greater concern is that this problem of extremely hot days is getting worse, as shown by weather records over the past two decades. This year the city recorded 68 days between June and August when the temperature climbed over 28.2 C. In 2007, 61 days were recorded above the threshold, up 10 percent over a decade. In 1997, 42 days were recorded, a 62-percent increase in two decades, according to the Hong Kong Observatory (HKO).

“Climate change has driven up ambient temperatures to a level that could debilitate human health, with our children suffering the most. The research just bore it out,” Chan added. 

This year the HKO revealed a number of worrisome statistics. In 2017 there were 41 hot nights with temperatures recorded at 28 C or higher. That figure is the highest in history, with only 23 and 12 hot nights tallied in 2007 and 1997, respectively. Worse, on Aug 22, a day before Typhoon Hato struck, the afternoon temperature rocketed to an all-time record of 36.6 C. This year was one of the hottest years since 1884 when records were first kept.

With the temperature rising at a rate of 0.15 C per decade in Hong Kong since 1987, the city’s annual mean temperature is expected to surge by around 1.5-3 C by 2060 and 3-6 C by 2100, relative to the 1986-2005 average of 23.3 C — unless greenhouse gas emissions are sharply curbed.

The effects of rising temperatures on human health are brought into sharper focus in a study by 24 international academic institutions and organizations. That research found that the higher frequency of heat waves and their longer duration had already exposed an additional 125 million people worldwide to greater health risks from heat between 2000 and 2016. The study found that people under prolonged exposure to high temperatures were more prone to heat stress, heat stroke, aggravated cardiovascular and renal conditions. Those at the greatest risk were the poor, the study concluded. The poor had the least defense against the heat when temperatures rose beyond a certain degree. The findings of the study were published in The Lancet, a British medical journal.

Lee, a child of an underprivileged family, may not know the statistics, but he knows that this year’s summer months were terrible for his young life. He was sick for most of the season, in which the summer flu battered him harder than ever and had him hospitalized for several nights.

“I had never seen hot days more scorching than last summer,” said Lee. “I always found myself lying on the bed, heaving, sweating, unable to sleep, dizzy, and very uncomfortable.”

In her study, Chan discovered an overall 4.5-percent increase in hospital admissions from 1998 to 2009 when daily mean temperature rose 1 C above the threshold of 29 C. As was the case with the mortality rate, the rate of hospitalization showed an exponential increase for further elevations of temperatures. 

Low-income families were proved to be more vulnerable, she said, explaining, “Families with more money can afford air-conditioning. Poor families can’t afford it.” 

Under the weather

A clearer way of understanding how people break down under hot weather is explained by Richard Fielding, professor of the School of Public Health at the University of Hong Kong.

He explains that “wet-bulb” temperature is a useful way of sizing up the hazards of extreme heat on the human body. Wet-bulb temperature, as the name implies, involves wrapping a wet cloth around a thermometer bulb. The reading takes account of moisture in the air, which gives a more accurate index of the heat effect on the human body.

Fielding elucidates that while the normal core temperature is around 37 C, the temperature on skin surface is normally 2 C lower at 35 C.

The wet-bulb temperature at 35 C is about as much as the human body can stand. Above that it is impossible for the body to cool itself through sweat, the evaporation of which normally has a cooling effect. Heat becomes trapped inside the body. The temperature climbs. As the body absorbs more heat from the surrounding environment than it is capable of dissipating, hyperthermia sets in. Then come heat cramps, exhaustion and, at the worst, lethal heatstroke. For that reason the wet-bulb temperature of 35 C is sometimes referred to as the survivability threshold.

“When people get to a wet-bulb temperature of 35 C, if they can’t get out of that temperature they will die of heat stress after six hours, even if they are drinking a lot of water,” Fielding stressed.

In 2015, a severe heat wave with a wet-bulb temperature at 50 C — 15 C above the safety limit — swept India and Pakistan. More than 3,500 people died in the two regions where there was no air-conditioning and no relief from the heat even in public areas.

Hong Kong hasn’t seen days with the wet-bulb temperature over 35 C yet. However, given the trend toward increasing temperatures the future gives cause for concern. The HKO projects that the annual number of very hot and humid days in town, with a maximum wet-bulb temperature of 28.2 C or above, is expected to hit 96 days by the end of this century — compared to the current nine days — if greenhouse gas concentration continues to escalate.

The projection is calculated according to the formula of Representative Concentration Pathways (RCP). It’s an opaque-sounding term. Simply stated, it’s the calculation of the amount of solar radiation that penetrates the earth, related to the amount of heat reflected by the earth back into space. The calculation is recorded in terms of watts per square meter (W/m2). Climatologists predict a worst-case scenario, aka the RCP 8.5 scenario, in which extra heat of 8.5 W/m2 will be trapped in the earth, raising global temperatures 4.1-4.5 C above pre-industrial levels — that is if greenhouse emissions stay unchecked by 2100.

South Asia is especially susceptible to the onset of torrid conditions. It’s already one of the hottest regions of the planet. Between 2071 and 2100, an estimated 4 percent of the population in Pakistan, Nepal, India, Bangladesh and Sri Lanka will experience  deadly, six-hour heat waves with wet-bulb temperatures exceeding 35 C at least once. It is inevitable under the RCP 8.5 scenario as reported in the journal Science Advances earlier this year.

  

Young and old

The survivability threshold at 35 C applies to people already in good health. For children and the elderly, especially those who are poor, 35 C may already surpass the survivability limit. Temperatures of a few degrees below that can still be life-threatening.

Aggravating these circumstances is the well recognized fact that global warming is also associated with increased pollution. Copious residues from fossil fuels are pumped into the atmosphere, like ozone, sulfur dioxide and nitrogen dioxide. Increased warming over prolonged periods also causes plants to release more pollen into the atmosphere.

In the increasingly polluted air linked to climate change, children are the most vulnerable. They inhale more air in proportion to body weight than adults. As such, children ingest more pollutants with every breath. Their respiratory systems are still developing, thus they absorb a higher amount of toxic materials. Many of these toxins are retained in the body, depleting children’s health, said Chan.

As a result, asthmatic children are more likely to suffer more frequent attacks, while people with emphysema and bronchitis are more likely to suffer aggravated respiratory diseases.

In the case of infectious diseases, hot weather becomes a virulent breeding ground. In Hong Kong, the elderly aged 75 or above were found to be most vulnerable, with a 9.6-percent higher risk of hospitalization for contagious illnesses, relative to 3.7 percent for the youngest group (aged under 15).

Most elderly people have already developed chronic diseases like diabetes, high blood pressure and cardiovascular diseases, which have degraded their immune systems’ ability to withstand infectious diseases, Chan explained.

A torrid time

At his home, the little boy picked his way around the miniature flat and flopped down on the bottom mattress of the bunk bed which takes up two-thirds of the flat’s space.

Lee is young, but he has long known his life is always about a math formula: income minus expense.

He and his mother receive a monthly allowance of HK$4,700 from the government. The midget digs, with hardly a space to walk in, costs them HK$3,400 a month. Thus, only HK$1,300 is left to feed two mouths.

“I had to run the air-conditioner on the hottest nights just to let my son go to sleep,” said Tao, whose husband died of lung cancer seven years ago.

She eked out HK$300 a month, over 20 percent of the household income, to give Lee air-conditioned nights. 

In Hong Kong, low-income families living in subdivided flats like Lee’s household are particularly defenseless against global warming, said Fielding of HKU.

“Good ventilation is a determinant of good health,” he stressed, adding, “Imagine living in a cage home without fresh air. It doesn’t only trap the heat, but pollutants, viruses and bacteria, and people there will be infected more readily.”

The warming climate also favors the flourishing of particular strains of bacteria. E. coli, the most common bacteria causing diarrhea in children worldwide, grows at its highest rate at 37 C, equal to the human core temperature.

In 2016, a group of scientists discovered that a 1 C increase in monthly mean temperature had led to a rise of 8 percent in incidence of E. coli in Bangladesh. The study, published in the Journal of Infectious Diseases last year, predicted the tally will climb. An estimated 800,000 new cases of  E. coli-related diarrhea are expected to emerge, as temperatures are projected to increase by 0.8 C between 2016 and 2035.  

Climate change has led to a global increase in the transmission of dengue fever by the mosquito Aedes aegypti of around 9.4 percent relative to 1950 levels, according to The Lancet report in 2017.

Aedes aegypti is not found in Hong Kong but the city’s prevalent species Aedes albopictus is also a carrier.

“The global warming temperatures are expanding the favorable habitats mosquitoes can encroach on and infect humans by biting them,” explained Fielding.

Even a milder scenario RCP 4.5 could still be devastating. It’s a situation that still arises assuming CO2 emissions peak around 2040 and decline by 2100, limiting temperature increases to 2 C above pre-industrial levels by 2100 — just as stipulated in the Paris Climate Agreement. Under that condition, the annual mean temperature in Hong Kong is still projected to rise by 1-2 C by 2060, and by 1.5-3 C by 2100, relative to the 1986-2005 average of 23.3 C.   

Gabriel Lau Ngar-cheung, professor of the Department of Geography and Resource Management at the CUHK, said the city’s poorest are the least adaptive to the warming climate.

“A 1 C increase affects the well-off only marginally. They could turn the air-con cooler as they like,” Lau said. “But for people living at the subsistence level, it could mean real suffering as they coudn’t afford resources like air-conditioning to ward against the damaging heat.”

The uncertain future 

Tao and Lee hang around places only within walking distance. They rarely travel outside Sham Shui Po. Lack of money doesn’t allow it.

The mother, who does not have permanent residency, stays in Hong Kong on a Visit Visa. She is forbidden to work in town.

Lee slipped on his new sneakers before heading to the community center of the Society for Community Organization, an NGO that has provided furniture, computer equipment, food and a refuge from the heat to the family for years.

“I cherish this pair of shoes. They cost over HK$100,” he said looking down at the shoes, his features lit up with a fond smile and an expression of awe. As winter is coming in, his mother bought him the new pair so he can prance around the basketball court — Lee’s favorite activity which he had sat out due to the extreme heat sickening him in summers.

Tao smiled back, watching her son parade around. Silently she’s worried that Lee has become physically debilitated by the hot summers. She is beset by free-floating anxieties, like whether he might be sick on an exam day, causing his academic standing to crash. That is a worry that casts a long shadow far into the future over the enduring hope that Lee’s success in his schooling may help them break out of the lingering cycle of poverty.

In the years to come, the sun is likely to blaze even hotter. The suffering of Lee’s family may increase, along with 1.35 million other Hong Kong residents struggling below the poverty line.

The possibility

Emily Chan of the CUHK argued Hong Kong’s government is not well prepared for the growing health menace of climate change.

As to vigilance against extreme hot weather, HKO issues the “Very Hot Weather” warning over radio and television to alert the public to stay hydrated and away from long exposure to heat. Forty daytime community centers and 15 temporary night heat shelters were offered to citizens to seek refuge from heat this year.

Chan believes large numbers of children and the elderly have been heedless of the underlying threats of hot weather warnings and unaware that there are shelters.  

As of November 2017, the global CO2 level averages 407.22 ppm — the highest for 650,000 years, it is estimated. The CO2 emissions have been trapping the solar heat, and have heated up the global temperature by 1.2 C since 1880. Last year, the world saw the warmest ever surface temperatures — 0.99 C hotter than the mean of the mid-20th century, according to US space agency NASA.

As air temperatures continue to rise, Chan expects the tally of people coming down with heat-related illness will grow and the mortality rate will go up, on the basis of her earlier findings.

“But these casualties can be minimized if the HKSAR would like to strengthen the mitigatory approaches to protect the heat from harming vulnerable populations again,” she added.

She urged the government to expand outreach services to the needy, like poor families and street sleepers in the city’s poverty-stricken districts, once the hot weather warning is raised. Cooling appliances like fans and air-conditioners should be given to the impoverished to help them get through the sweltering days, she added.

By 2030, the HKSAR expects to ramp up renewable energy to 3-4 percent of all energy produced, according to the Climate Action Plan 2030+ published this year.

However, Richard Fielding of  HKU contended that this vision does not go far enough. The government, he said, needs to push that boundary higher to build more renewable energy plants to phase out the coal sector.

Contact the writer at honeytsang@chinadailyhk.com


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