Encyclopedia of Environmental Science and Engineering, Volume I and II

AIR POLLUTANT EFFECTS 41

Hypersensitivity pneumonitis and humidifier fever also

are associated with aerosols from contaminated water. The

former, which is the more serious, is an interstitial lung dis-

ease that in its acute form causes fever, chills, cough, and

dyspnea 4 to 6 hours after exposure. The more commonly

blamed agents are the thermoactinomycetes or the thermo-

phylic micropolyspora. Humidifier fever is self-limited, with

symptoms resembling the flu.

FUNGAL DISEASES

Fungi can cause disease and can also generate highly potent

toxins. Treating the diseases is a special problem because

available drugs are few in number because of the difficulty

of finding ones that will preferentially attack fungal cells in

the presence of mammalian cells.

Histoplasma capsulatum and other molds and yeast organ-

isms such as blastomyces, cryptococcus, and coccidiodes are

pathogenic to humans. The latter is responsible for valley

fever, which is causing concern in hot, dry areas such as the

Southwest, where it thrives. Cryptococcus, often found in soil

contaminated by pigeon droppings, is a killer of AIDS patients,

attacking the central nervous system and causing meningitis.

Aspergillus fumigatus is a common fungus that invades the

lung. When the spores are stirred up and inhaled they can grow

fungus balls in the lung. One condition is called “farmer’s

lung,” but in hospitals where transplant or AIDS patients have

suppressed immune systems, the fungus can produce severe

infections that must be treated rapidly. Detection of the fungus

is difficult because instead of using the bloodstream it attacks

by traveling from tissue to tissue. Aspergillus flavus produces

aflatoxin, one of the most potent carcinogens known.

As in the case of tuberculosis, immuno-compromised

individuals are readily susceptible to the acquisition of dis-

ease via inhalation. Nosocomial aspergillosis from sources

such as contaminated air conditioners should be a special

concern in hospitals.

ASBESTOS

“Asbestos” is the generic term for silicate materials that occur

in fibrous form. A fibrous form that is classified as a serpentine

is called “chrysotile” and is the type of asbestos most common

in the United States. The length and flexibility of its fibers

allow it to be spun and woven. Other types of asbestos are

amphiboles that include amosite, crocidolite, tremolite, anto-

phyllite, and actionide. Their fibers do not lend themselves to

weaving, but in general they have higher heat resistance than

chrysotile. Asbestos is used in many products, but most of it

is used in construction—in floor tiles, cements, roofing felts,

and shingles—and was used in very large quantities to protect

steel structures from weakening during fires.

Measurements made of asbestos concentrations in the

ambient air of New York City led to its banning in 1971 in spra-

yed material, a ban rapidly adopted nationally and worldwide.

Nevertheless, many tons of asbestos will have to be handled

with great care when the many buildings that used it to pro-

tect their steel structure from fire are finally demolished.

A study by Selikoff et al. of mortality among 17,800

asbestos workers from 1967 to 1976 found 675 excess deaths

from cancer out of a total of 995. The ratio of observed to

expected deaths in such a population was 3.11 for all cancers,

4.60 for lung cancers, and greater than 1 for several other

TABLE 3

Relative sensitivity of plants to SO 2

Crops

Sensitive Tolerant

Alfalfa Sweet potatoes Celery

Buckwheat Lettuce Corn

Barley Beans Onion

Cotton Broccoli Potato

Red clover Squash Cabbage

Oats Wheat —

Peas Carrot —

Spinach Tomato —

Flowers

Sensitive Tolerant

Sweet pea Sweet William —

Four-o’clock Gladiola —

Cosmos Tulip —

Bachelor button Violet —

Aster Zinnia —

Trees

Sensitive Tolerant

Trembling aspen Alder Cedar

Jack pine Red pine Citrus

White pine Austrian pine Maple

White birch Hazel Linden

Larch Apple —

Large-toothed aspen Douglas fir —

Willow Ponderosa pine —

Garden plants

Sensitive Tolerant

Peas Cucumber Muskmelon

Rhubarb Lettuce Corn

Spinach Radish Onion

Swiss chard Squash Potato

Beans Tomato Cabbage

Beets Cultivated mustard Broccoli

Turnips Kohlrabi —

Carrot —

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