Page 9 - Volume 2, Issue 1, January 2009

Pesticide exposure risks

7

models. Extrapolations often have to be

made using data from the most suitable or

similar scenario for crop or application tech-

nique. In selecting an indicative value for po-

tential dermal exposure the variability of the

data in the database supporting the model

needs to be considered. The UK model uses

the 75th percentile values, whereas the Ger-

man model uses the geometric mean val-

ues. Having determined the potential op-

erator exposure, a number of assumptions

are then made with respect to transfer fac-

tors of the pesticide from the outside of PPE

to the skin of the operator and the rate of

subsequent dermal absorption of the active

substance estimated to have reached the

skin of the operator.

Performance of protective clothing

The protection factor offered by vari-

ous types of PPE tends to be related to the

performance of new garments in standard

laboratory tests such as EN 463 and EN 468.

These two tests are for whole garments of

chemical protective clothing and those

passing the test are CE marked as Type 3 (EN

463) or Type 4 (EN 468) garments. Type 4

garments offer more protection than Type 3

garments. Recently Type 6 garments (prEN

13034) became available, which offer limit-

ed protection against penetration by liq-

uid contamination. However in many cases,

such as with the orchards or greenhous-

es of southern Europe, working conditions

for pesticide operators are such that spe-

cific chemical protective clothing is rare-

ly used. Where protective clothing is worn

it tends to be workwear such as polyester

cotton coveralls, for which there are no test

methods to determine penetration by aque-

ous liquids. Field and laboratory tests car-

ried out within the framework of the proj-

ect SMT4-CT96-2048 have shown that the

rate of coverall contamination is a key fac-

tor in determining the protection factor of-

fered by various types of coveralls (Moreira

et al.

, 1999).

Another factor which should be further

evaluated is the age or condition of PPE. Dis-

posable coveralls have a limited life, and the

coating on the material begins to be dam-

aged and removed by contact with the crop

for example, or simply through the move-

ment of the applicator creasing the materi-

al. Washable coveralls such as the polyester

coveralls become more absorbent and less

repellent after repeated washings, as the

coating of the material is removed.

Rates of dermal absorption

Most models assume that 10% of the ac-

tive substance which reaches the skin is ab-

sorbed into the body. In practice the pro-

portion of the active substance which is

absorbed by the body is influenced by many

factors. These range from factors such as the

physicochemical properties of the active

substance (partition coefficient in octanol/

water and molecular weight), concentration

of the active substance on the skin and the

area of skin exposed, to the relative humid-

ity and temperature of the air. In order to

improve model estimates of exposure, com-

pound specific data are required for dermal

absorption for likely ambient conditions in

which the product would be used. The type

of formulation can affect the rate of der-

mal absorption, such as the presence of li-

pophilic organic solvents such as xylene in

emulsifiable concentrate formulations. The

size of the molecule of the active substance

also affects the rate of dermal absorption.

Biomarkers of exposure and effect

Biomonitoring studies to measure pesti-

cides and metabolites in urine samples give

an indication of the exposure levels and the

absorbed dose, assuming pharmacokinet-

ic data are available. Biomarkers of expo-

sure can also measure the interactions be-

tween a pesticide and target molecules or

cells, including detection of biologically ef-

fective doses (Lowry

et al.

, 1995; Decaprio

et

al.

, 1997; Lopez

et al.

, 2007).

Biomarkers of effect can identify alter-

ations of an organism that could indicate a

potential for health impairment or disease.

Therefore biomarkers can be used to de-

tect the early effects of pesticides before

adverse clinical health effects occur. Tech-