Environmental Engineering Reference
In-Depth Information
The label must also include a signal word and sometimes symbol that
states how toxic the pesticide actually is. Signal words vary slightly, but
in any language they must indicate the relative level of health risk the
product presents. Typical words are 'highly toxic' (in many countries
indicated also by the skull-and-cross-bones symbol), 'danger', 'poison',
'warning', 'caution', etc. Pesticide toxicity is usually expressed as
lethal
dose value
or LD
50
, which is the amount of the material in milligrams per
kilogram of body weight required to kill 50% of a test population of
laboratory animals. Pesticides with low LD
50
are the most toxic. For
example, the soil fumigant methyl bromide has an LD
50
value around 2,
whereas that of the herbicide benefin is above 5000. These figures means
that a human weighing 50 kg who ingested 100 mg of methyl bromide
would have only a 50% chance of surviving (2 mg/kg
100 mg).
The same human would have to ingest 0.25 kg of benefin to suffer the
same risk (5000 mg/kg
50 kg
¼
250,000 mg or 0.25 kg). LD
50
values are
usually not printed on the label but are reflected in the signal words that
appear there. The term 'highly toxic' usually corresponds to an LD
50
between 0 and 50, 'moderately toxic' to one from 50 to 500, 'modestly
toxic' to one from 500 to 5000, and non-toxic to one above 5000. If the
product is harmful to swallow or inhale or can damage eyes or skin, the
label often includes emergency first-aid measures and explains exposure
conditions requiring medical attention. In many countries labels also
include instructions about avoiding harm to the environment, like such
statements as 'Toxic to bees' or 'Do not apply where run-off is likely to
occur'.
Most pesticide labels include directions for use. This section provides
information on how to use the product properly within legal require-
ments to get the best results. The directions for use state what pests the
given product is registered to control, give the form in which the product
should be applied, list and describe required application equipment,
provide mixing instructions, recommend a frequency of application,
and so on. The law sometimes requires that the producer's name and
address be printed on the label, along with an establishment number
identifying the factory that made the chemical.
50 kg
¼
Applying pesticides
Most pesticides used in turf-grass management are applied in the form
of liquid sprays or solid dry granules. Because methods of pesticide
application can affect human health as well as the environment, in many
countries the law regulates pesticide application procedures. Some pes-
ticides that are especially harmful to humans and the natural environ-
ment can be applied only by trained and licensed pesticide applicators.
