Home Kelly Alexander, Sr. Papers Concerning the NAACP, 1948-1998 naacp-ms508-0208023-050
Memoranda and "Economic Empowerment"
naacp-ms508-0208023-050
Environmental Cancer Risks
Environmental causes probably account for well over
half of all cancer cases. Most environmental risks are
determined by lifestyle choices (smoking, diet, etc.),
while the rest arise in community and workplace
settings. The degree of cancer hazard posed by these
voluntary and involuntary risks depends on the concentration or intensity of the carcinogen and the exposure
dose a person received. In situations where high levels
of carcinogens are present and where exposures are
extensive, significant hazards may exist, but where
concentrations are low and exposures limited, hazards
are often negligible. However, when low-dose exposures
are widespread, they can represent significant public
health hazards (for example, secondhand tobacco
smoke). Strong regulatory control and constant attention
to safe occupational practices are required to minimize
the workplace potential for exposure to high-dose
carcinogens.
Risks are assessed to protect people against unsafe
exposures and to set appropriate environmental
standards. The process of risk assessment has two steps.
The first identifies the chemical or physical nature of
a hazard and its cancer-producing potential, both in
clinical and epidemiologic studies and in laboratory tests
using animals or cell systems. Special attention is given
to any evidence suggesting that cancer risk increases
with increases in exposure. The second step measures
levels of hazard in the environment (air, water, food,
etc.) and the extent to which people are actually exposed
(how much they eat of a particular food, use a particular
water source, etc.). Knowledge of how the body absorbs
chemicals or is exposed to radiation is essential for such
dose measurements.
Unfortunately, evidence of risk for most potential carcinogens is usually the result of high-dose experiments
on animals or observations where high-dose exposures
have occurred in humans. To use such information to set
human safety standards, scientists must extrapolate from
animals to humans and from high-dose to low-dose
conditions. Because both extrapolations involve much
uncertainty, conservative assumptions are used so that
risk assessment will err on the side of safety. For cancer
safety standards, only increased risks of one case or less
per million persons over a lifetime are usually acceptable.
Safety standards developed in this way for chemical or
radiation exposures are the basis for federal regulatory
activities at the Food and Drug Administration, the
Environmental Protection Agency, and the Occupational
Safety and Health Administration. The application
of laws and procedures by which standards are
implemented and risks are controlled is called risk
management.
Various chemicals show definite evidence of human
carcinogenicity (for example, benzene, asbestos, vinyl
chloride, arsenic, aflatoxin) or are probable human
carcinogens based on evidence from animal experiments
(for example, chloroform, dichlorodiphenyl-
trichloroethane [DDT], formaldehyde, polychlorinated
biphenyls [PCBs], polycyclic aromatic hydrocarbons).
Often in the past, direct evidence of human carcinogenicity has come from studies of workplace conditions
involving sustained, high-dose exposures. Occasionally,
risks are greatly increased when particular exposures
occur together (for example, asbestos exposure and
cigarette smoking).
Only high-frequency radiation, ionizing radiation (IR)
and ultraviolet (UV) radiation, has been proven to cause
human cancer. Exposure to sunlight (UV radiation)
causes almost all cases of basal and squamous cell
skin cancer and is a major cause of skin melanoma.
Disruption of the earth's ozone layer by atmospheric
chemical pollution (the "ozone hole") may lead to rising
levels of UV radiation.
Evidence that high-dose IR (x-rays, radon, etc.) causes
cancer comes from studies of atomic bomb survivors,
patients receiving radiotherapy, and certain occupational
groups (for example, uranium miners). Virtually any part
of the body can be affected by IR, but especially bone
marrow and the thyroid gland. Diagnostic medical and
dental x-rays are set at the lowest dose levels possible to
minimize risk without losing image quality. Radon
exposures in homes can increase lung cancer risk,
especially in cigarette smokers; remedial actions may be
needed if radon levels are too high.
Unproven Risks
Public concern about environmental cancer risks often
focuses on risks for which no carcinogenicity has been
proven or on situations where known carcinogen
exposures are at such low levels that risks are negligible.
CANCER FACTS & FIGURES 1997
Title Memoranda and "Economic Empowerment"
Subseries Subseries 4, Committees
Date Created 1997-1998
Box Number 8
Title naacp-ms508-0208023-050
OCR Transcript Environmental Cancer Risks Environmental causes probably account for well over half of all cancer cases. Most environmental risks are determined by lifestyle choices (smoking, diet, etc.), while the rest arise in community and workplace settings. The degree of cancer hazard posed by these voluntary and involuntary risks depends on the concentration or intensity of the carcinogen and the exposure dose a person received. In situations where high levels of carcinogens are present and where exposures are extensive, significant hazards may exist, but where concentrations are low and exposures limited, hazards are often negligible. However, when low-dose exposures are widespread, they can represent significant public health hazards (for example, secondhand tobacco smoke). Strong regulatory control and constant attention to safe occupational practices are required to minimize the workplace potential for exposure to high-dose carcinogens. Risk Assessment Risks are assessed to protect people against unsafe exposures and to set appropriate environmental standards. The process of risk assessment has two steps. The first identifies the chemical or physical nature of a hazard and its cancer-producing potential, both in clinical and epidemiologic studies and in laboratory tests using animals or cell systems. Special attention is given to any evidence suggesting that cancer risk increases with increases in exposure. The second step measures levels of hazard in the environment (air, water, food, etc.) and the extent to which people are actually exposed (how much they eat of a particular food, use a particular water source, etc.). Knowledge of how the body absorbs chemicals or is exposed to radiation is essential for such dose measurements. Unfortunately, evidence of risk for most potential carcinogens is usually the result of high-dose experiments on animals or observations where high-dose exposures have occurred in humans. To use such information to set human safety standards, scientists must extrapolate from animals to humans and from high-dose to low-dose conditions. Because both extrapolations involve much uncertainty, conservative assumptions are used so that risk assessment will err on the side of safety. For cancer safety standards, only increased risks of one case or less per million persons over a lifetime are usually acceptable. Safety standards developed in this way for chemical or radiation exposures are the basis for federal regulatory activities at the Food and Drug Administration, the Environmental Protection Agency, and the Occupational Safety and Health Administration. The application of laws and procedures by which standards are implemented and risks are controlled is called risk management. Chemicals Various chemicals show definite evidence of human carcinogenicity (for example, benzene, asbestos, vinyl chloride, arsenic, aflatoxin) or are probable human carcinogens based on evidence from animal experiments (for example, chloroform, dichlorodiphenyl- trichloroethane [DDT], formaldehyde, polychlorinated biphenyls [PCBs], polycyclic aromatic hydrocarbons). Often in the past, direct evidence of human carcinogenicity has come from studies of workplace conditions involving sustained, high-dose exposures. Occasionally, risks are greatly increased when particular exposures occur together (for example, asbestos exposure and cigarette smoking). Radiation Only high-frequency radiation, ionizing radiation (IR) and ultraviolet (UV) radiation, has been proven to cause human cancer. Exposure to sunlight (UV radiation) causes almost all cases of basal and squamous cell skin cancer and is a major cause of skin melanoma. Disruption of the earth's ozone layer by atmospheric chemical pollution (the "ozone hole") may lead to rising levels of UV radiation. Evidence that high-dose IR (x-rays, radon, etc.) causes cancer comes from studies of atomic bomb survivors, patients receiving radiotherapy, and certain occupational groups (for example, uranium miners). Virtually any part of the body can be affected by IR, but especially bone marrow and the thyroid gland. Diagnostic medical and dental x-rays are set at the lowest dose levels possible to minimize risk without losing image quality. Radon exposures in homes can increase lung cancer risk, especially in cigarette smokers; remedial actions may be needed if radon levels are too high. Unproven Risks Public concern about environmental cancer risks often focuses on risks for which no carcinogenicity has been proven or on situations where known carcinogen exposures are at such low levels that risks are negligible. For example: 28 CANCER FACTS & FIGURES 1997
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