Assessing Chemical Hazards on Golf Courses
Before we can decide how concerned we should be about chemicals
in our environment, and on golf courses in particular, there are
some basic, common-sense rules that should be kept in mind.
First, any chemical can produce toxicity in living organisms.
Second, for a toxic effect to be produced, an organism must
actually be exposed to the chemical and the exposure must result
in a dose sufficient to produce toxicity. In other words, the
dose makes the poison. Third, chemicals have specific and
These simple facts are often misunderstood in our society. Many
assume, incorrectly, that the mere presence of a chemical
constitutes a health threat. Yet we all know this is not true. If
the mere presence of a chemical in our environment could produce
health effects, then aspirin could relieve headaches without
being swallowed. If the dose did not determine the poison, one
glass of wine would be as inebriating as an entire bottle, and it
would make no difference if the wine was swallowed or poured on
one's feet! If chemicals did not have specific and
predictable effects, their use as medicines would be impossible.
Too often we fail to apply the common sense of dose and response
to chemicals with which we are unfamiliar.
Risk assessment is the application of these and other principles
of toxicology help us rationally decide our level of concern
about chemicals encountered in the environment. Risk assessments
are methods for comparing levels of chemicals in the environment
with doses that produced no adverse effects in laboratory animal
studies or environmental toxicity tests. These methodologies can
be applied to turfgrass systems to help ensure that chemicals are
used in amounts and frequencies that do not pose unacceptable
health or environmental hazards.
An example of the methodology used to assess the concern about
chemicals used on golf courses is illustrated here by considering
three pesticides applied to a putting green. Our approach is
consistent in principle with the Baseline Human Health Risk
Assessment used by the U.S. Environmental Protection Agency
(U.S.E.P.A.) to evaluate hazardous waste sites and chemical
contamination of soil, but is modified and refined specifically
for a putting green. Our assessment is preliminary in nature and
should in no way be considered thorough or complete. It is
intended only to illustrate some principles of health risk
assessment as applied to golf courses and is not a definitive
evaluation. Our goal was to suggest how risk assessment methods
can be used to address concerns regarding chemicals used on golf
courses. We utilized preliminary data to conduct a limited health
risk assessment for a putting green and illustrated how such
information can assist decision-making regarding levels of
chemicals that may warrant concern.
The first step in health risk assessment is to evaluate the ways
a person might come into contact with chemicals at a particular
site, in this instance a putting green, and to take measurements
of chemicals at those points of potential exposure. We evaluated
the potential exposure to three pesticides on a putting green for
a golfer who plays 18 holes of golf. We considered four pathways
of exposure for this golfer. We assumed that this theoretical
golfer would 1) kneel on the green to align putts, 2) handle golf
club grips that have been laid on the green, and 3) contact the
soles of golf shoes while cleaning them after the round. These
are dermal exposure pathways, i.e., those that involve absorption
of chemicals through the skin.
Because skin is an effective protective barrier against entry of
most chemicals into the body, very little chemical that contacts
the skin is actually absorbed in most instances. The dermal
permeability factor for a chemical reflects the fraction of
chemical applied to skin that might actually be absorbed.
Although oral exposure pathways would probably be less
significant for most golfers than dermal pathways, as an extreme
case we assumed that the golfer would 4) clean his golf ball by
licking it. This is an ingestion exposure pathway. We assumed
that all of the pesticide ingested is actually absorbed into the
body because the intestinal tract generally is not an effective
barrier to the absorption of organic chemicals.
For the sake of presenting a reasonable maximum exposure, we took
measurements 24 hours following application of diazinon,
chlorpyrifos (Dursban 2E), and isazofos (Triumph 4E) at rates of
470,57, and 229 mg active ingredient per square meter of turf.
The measurements were taken from a preliminary study conducted on
a Tifgreen bermudagrass surface at the Ft. Lauderdale Research
and Education Center, University of Florida, and the pesticide
analysis was conducted at the Everglades Research and Education
Center, Belle Glade, University of Florida. This research on
pesticide dislodgeability was sponsored by the Florida Turfgrass
Association and by the USGA Green Section.
We measured the amounts of pesticides retained on a) a 10 cm
square piece of cotton attached to one knee while kneeling for 10
seconds to simulate aligning a putt, b) a 10 cm square piece of
leather attached to a shoe sole following 10 steps on the treated
turf surface, and c) a golf ball putted 36 times over a distance
of 4 meters per putt. From the amount of pesticide retained on
leather shoe bottoms, we estimated the amount that might be
retained on leather golf club grips laid on the putting green.
Using the levels of pesticides listed in Table 1 for each
exposure point, we calculated the dose of each pesticide that a
golfer might receive from each of the exposure pathways and
summed the doses from all pathways to arrive at the golfer's
total dose. The equations used to calculate dermal and oral doses
are listed in. The golfer's total doses were then compared
with doses considered by the USEPA to be safe for a person to
receive every day for a lifetime (a dosage called the
"Chronic Reference Dose," or RfD). Chronic Reference
Doses take into account that toxicity can accumulate for some
chemicals in some organ systems when the chemical is received as
frequently as every day. Although we calculated single doses from
one round of golf, we compared these doses with chronic RfDs,
which are safe doses that can be received daily for a lifetime.
The comparison was made by calculating a "Hazard
Quotient," which is the person's total dose divided by
the RfD. Doses below the RfD yield Hazard Quotients less than 1,
and those greater than the RfD yield Hazard Quotients greater
than 1. If the calculated dose is equal to the "safe"
dose (RfD), then the Hazard Quotient equals 1.
In order to consider the entire putting green as a unit, we
summed the Hazard Quotients for all three pesticides to arrive at
a "Hazard Index" for the putting green. This takes into
account any potential for additive toxicity from two or more
chemicals. A Hazard Index less than 1 would indicate that the
person's dose of each pesticide is below its respective
"safe dose" or RfD, and that the additive potential
does not exceed a "total safe dose." The USEPA
considers a Hazard Index less than 1 to indicate that there is no
increased health risk. In other words, a Hazard Index less than 1
indicates that all contaminants are present at concentrations
below those that could cause effects in humans, even if the
chemicals have additive effects.
Under the assumptions of this risk assessment, the exposures
evaluated could be tripled without exceeding levels considered
safe for daily lifetime exposure. Because we compared the doses
our theoretical golfer might receive from one round of golf with
chronic RfDs, this golfer could receive these doses every day of
his life without concern for cumulative toxicity. We caution that
this "conclusion" is made as an example only and cannot
be applied generally because conditions and pesticide use can
vary widely from site to site.
The focused risk assessment presented here would indicate that
under these theoretical conditions and assumptions, a
golfer's exposures to chlorpyrifos, diazinon, and isazofos on
putting greens would be considered acceptable because the Hazard
Index is much less than 1. But how would we interpret a Hazard
Index greater than 1? Although a Hazard Index of 1 or less is
considered safe, it is not accurate to say that a Hazard Index
greater than 1 is therefore unsafe. Because of the large safety
factors often employed in developing Reference Doses (10 to
10,000), doses many times greater than the Reference Dose could
potentially be all right without adverse effects. A Hazard Index
greater than 1 indicates that we are less certain of the
potential for adverse health effects from contact with the site,
but it does not necessarily indicate that the site is a threat to
health. Hazard Quotients and Hazard Indices are interpreted
There are numerous sources of uncertainty inherent in the risk
assessment process. The extrapolation of toxicity data from
laboratory animal studies to human exposure scenarios is an
inexact science that introduces much uncertainty into the
process. Yet, it is upon these extrapolations that we must often
rely to determine doses that are safe from toxicity, such as
Reference Doses. Similarly. studies of chemical absorption are
rarely done on human subjects and may be the source of
considerable uncertainty in estimating chemical intakes. The
dermal permeabilities we used are rough estimates based upon
published studies, but a more thorough examination of the
literature may yield information that enables us to refine these
The assumptions we made regarding exposure events and durations
are worst-case scenarios and would apply to very few people.
Age-adjusted body weights are averages and actually fit only a
small number of people. Summing the toxicity scores (Hazard
Quotients) of various chemicals may overestimate potential health
risks from chemicals that target different tissues and organs.
Conversely, the potential for synergistic toxicity is not
directly considered in the risk assessment process.
The current means of addressing these uncertainties are through
extreme conservatism in all extrapolations and assumptions and by
the use of large "uncertainty factors" that reduce the
chemical dose considered safe. For example, determination of
Reference Doses is typically done by finding the dose at which no
effects are produced in rats or mice and dividing that dose by a
"safety factor" of 10 to 10,000. These safety factors
are used to account for uncertainty and to be sure that even the
most sensitive humans would not be adversely affected at the
Reference Dose. Use of such large safety factors may often result
in RfDs (safe daily doses) that are actually far below a dose
that could produce effects in humans. This approach is prudent
because the process of health risk assessment is intended to
support decision making that is protective of public health and
the environment rather than to accurately reflect the toxic
potential of chemicals.
Risk assessments are only as applicable and reliable as the data
upon which they are based. Without adequate data, our ability to
identify true health and environmental hazards is reduced and
anxiety over chemicals increases. In the absence of data that is
specific and complete, risk assessors must resort to conservative
assumptions to ensure that risk assessments overestimate rather
than underestimate chemical exposures and toxicities. Costly
errors can result when evaluations are made on the basis of
inappropriate or poorly documented data. The more accurate the
data we use to conduct risk assessments, the more confident we
can be that our efforts to protect the public and the environment
are appropriate and effective.
The risk assessment we report here, though limited in scope and
preliminary in nature, illustrates how the methodology can be
applied to turfgrass on golf courses. In order to expand and
complete this risk assessment, it is necessary to broaden its
scope and to reduce uncertainties inherent in its assumptions. To
do this, we must verify and expand the database on pesticide
fate, transport, dislodgeability and toxicology, and on human
behaviors that result in potential exposure. These data are
optimized for risk assessments on golf courses when turfgrass
scientists and toxicologists collaboratively design the
gathering, testing, and analysis of the data. This risk
assessment represents our initial efforts to expand the exposure
database and refine the risk assessment methodology for use in
golf course management.
Agency for Toxic Substances and Disease Registry (1992) Public
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U.S. Environmental Protection Agency (1992) Dermal Exposure
Assessment: Principles and Applications. Interim Report.
Fear of chemicals in the environment ranks high on the list of
anxieties for many Americans. Because this concern extends to
nearly every industry and activity in our society today, it
should come as no surprise that fears have arisen in regard to
chemicals used on golf courses, such as pesticides.