Urban Climate and Human Health

Temperature, Relative Humidity, Wind and Sunshine are the four elements most directly affect human’s physical and mental condition.

To maintain a constant core temperature of 37°C (98.6°F) of precondition to the well-being of all homothermous (warm-blooded animals). This requires continues physiological and behavioral adjustments to balance energy exchanges between the body and the environment.

Physiological adaptation and technology have permitted human settlement in climate zones well beyond the likely original warm human birthplace.

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Diversity in adaptations may be attributed to particular combination and weightings within seven interlaced groups of adaptation strategies

to atmospheric thermal, and stimuli. (handout)

1. Physiological adjustments: minor vasomotor to major sweating and metabolic responses.

2. Acclimatization (including habituation) of both physical and psychological mechanisms by periodic exposure to thermal stimulus.

3. Food energy intake and dietary alterations4. Metabolic alterations in scheduling of activities, selection and curtailment of

particular tasks or their sequencing.5. migration, either temporary or permanent avoidance of particular stress

conditions.6. clothing and building fabric interposition between the source of stress and

the organisms.7. external energy generation for space heating and cooling.

1,2,3 are involuntary and 4-7 voluntary. Overall, a precondition to human well-being in terms of both productivity and health appears to be the achievement of a harmonious balance between minimization of physiological responses in 1. and maximization of acclimatization in strategy 2.

Energy balance of a body

(M+Q)+/- R +/-C –E = +/-S (wm-2); M is metabolic heat minus energies used in work; Q is shortwave solar radiation income; R are longwave radiation; C is convection and E is evaporation. S is storage within body tissue (=0 over time).

Most favorable temperature for a person’s engaged in active work either indoor or outdoor is about 64°F (less fatigue). (differ somewhat for individual).

However, frequent moderate changes in temperature are stimulating, especially change to cooler weather. For example, autumn with moderate temperature changes in cooler is more favorable than spring. Long cold or hot spells are alike depressing.

Duration of extreme temp is very important (significant). statistics indicate that death rate is lowest when mean temp is 60-75°F. Some diseases like Malaria, yellow fever, etc are directly limited by temp (low temp).

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Table 17.3 Wind-chill Equivalent temp (Oliver, Climatology, p327).

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Humidity and air movement• Moderate humidity is more comfortable and healthful than very dry or very

moist. High humidity in high temp increase the conduct of heat to human body and at same time retards evaporation (body cannot cool off readily and more oppressive).

• High humidity in cold weather increases the conduction of heat from the body and intensity the feeling of cold. (high humidity feels warmer in hot weather and colder in cold weather).

• Hot wind increases perspiration to the physiological limit, resulting in fever and death (draw more heat than the body can be produced for normal evaporation).

• Humidity is especially related to respiratory diseases, such as pneumonia, influenza, and bronchitis. There are more prevalent in winter, owing not so much to low temperature but to low humidity existing in homes, office and hospitals in cold weather, to the spreading of infections, facilitated by indoor living. (If air temp is 0°F, indoor temp is 70°F without extra water supply, air is drier than the winds of Sahara).

Sunshine and health• Healing and disinfecting action of sunlight has long been

known, especially in UV portion of solar spectrum. A certain moderate intensity of sunshine is as essential to human and animal life as it is to plant life. Tubercle bacilli became harmless under direct ray of sun for an hour (bacteria causing tuberculosis).

• Excessive UV is harmful to skin (UV has three parts: A, B, C).

• UV-C, absorbed by O3; UV-B and UV-A, produce vitamin D, necessary for prevention of bone disease.

NOAA and EPA developed an ultraviolet index forecasting for 58 US cities. Table 17.4, Description of skin phototype

Table 17.5, Range of minute to burn for difference index values, P319.

Seasonal Affective Disorder (SAD): mood disturbance related to seasons. Most common form is winter depression, marked by sadness, decreased physical activities, weight gain, decreased libido (desire, urge, sex drive), and even interpersonal conflict.

Climatotherapy: the utilization of prevailing climate as therapeutic. (travel , Florida homes, Mediterranean yachts).

Illness related to sunshine

Ideal weather• Very few diseases are directly caused by weather or climate, but

condition of the atmosphere in which man lives often influences profoundly his vitality and his susceptibility to infection. Some air conditions are an aid to health and activity; some are a hindrance. Hot, humid, tropical climates appear to be the most unfavorable, and white men cannot live for long periods in such climate, without a general lowering of energy and of ability to resist disease.

• Idea weather defined as (1) daily mean temp of about 65°F (2) relative humidity continuously moderate, 50 to 60% (3) moderate to brisk air movement (4) abundant sunshine, but not monotonously cloudless and arid weather.

In short, our bodies, though capable of withstanding considerable extremes, are best adapted to average or intermediate conditions.

Temperature range for lowest human mortality• 21-27° C (White 1985) theoretically. • Lowest mortality related to stroke is 15.5-26.6°C (Rogot and Padgett, 1976).• It has regional differences of temp-related mortality, for example 14.3-

17.3°C in north Finland, but 22.7-25.7°C in Athens (Kalkstein). • Acclimatization: is the physiological adaptation of an animal or plant to

changes in climate or environment, such as light, temperature, or altitude. In other words acclimatization is the gradual accommodation of the body to changes in weather conditions.

• Respond of mortality to heat wave is strongest in temperate climate where hot days are not common. No increased mortality in warm regions where summer is consistently hot (Phoenix, Tampa).

• The same intensity of heat early in season produced much higher excessive mortality than occurs later in the season-intraseasonal acclimatization. Also, inter-seasonal acclimatization is also apparent (Kalkstein and Davis).

Climate and culture• All the people living in a given part of the world

are subject to its favorable or unfavorable climatic conditions for many generations. Thus the influence is accumulative and shows themselves in the energy, physical, and social condition and civilization of the people.

• Climatic hypothesis of civilization: highest civilization is possible only under the most favorable climate, a map of civilization today is a climatic map.

Tropical region Polar region

Food Fruits (bananas, coconuts, breadfruits)

Fish, flesh and fat of animals

Soil Soil production is abundant and spontaneous

Impossible for agriculture

activities Fishing, hunting, and reindeer breeding

Health Encourages indolence by its energetic activity unnecessary

Eye diseases due to dazzling snow outdoor and smoke indoor; death are mostly related to snow storms, freezing or drowning (high during sealing season)

Housing, clothing Shelter and clothing easily met

Close, unventilated dwelling and heavy clothing of skin and furs provided by hard labor and much danger

Life Too easy, no stimulus to activity

Too hard, no possibility of accumulation and leisure

Influence of extreme climates:Extremely adverse weather has influence on clothing, food, dwellings, customs, and occupations.

Climate and Beginning of civilization•Man began to make progress toward civilization and refinement in the less enervating portion of tropical or semitropical regions, where it is possible for him to obtain leisure.

• Then gradually moved into colder regions as man increases his knowledge of how to make a living on earth and protect himself from adverse weather conditions.

• Some of the earliest well-developed types of culture were in the valleys of Nile and of the Tigris and Euphrates Rivers, under arid, semitropical conditions where agriculture production and the accumulation of food were comparatively easy, except that agriculture required irrigation and, hence coordinated effort and organized society.

• Then center of civilization moved to Greece, then to Italy, and later, northward through Europe into increasingly stimulating climates, from Spain and Portugal to Holland, Great Britain, and Scandinavia

Ellsworth Huntington’s study (1915) on influence of temp, humidity and other weather elements upon individuals and small groups, found the best climates meeting the requirements are in a belt of the NH includes most of Europe, the British Isles, and greater part of the US, a narrow strip of southern Canada, and Japan (highly civilized nations of today).

Within a zone where mean annual temp is 40-70°F, called the temperature of civilization. It seems to indicate that present-day progress, characterized by energy and movement, is largely conditioned upon the stimulating, invigorating climate of the middle temperate regions of the globe. “Among the physical stimuli which may control human efficiency, none is more potent than climate” (Huntington’s statement).