Page 5 - Volume 2, Issue 1, January 2009

Pesticide exposure risks

3

the dermal exposure. The concentration of

the pesticide in the air inhaled by the opera-

tor is used as the basis for estimating opera-

tor exposure by the inhalation route. Partic-

ulates of up to 100 μm within the breathing

zone of the operator may enter the nose or

mouth. However, only particles of diameter

<10 μm range are likely to reach the lungs,

known as the inhalable fraction. The larg-

er particles will be deposited on the sur-

face and hairs of the nasal cavity, and subse-

quently swallowed in many cases.

Methodology to determine levels of

operator exposure

Dermal Exposure

Early methods of measuring potential

dermal exposure involved the use of absor-

bent cotton pads attached to different parts

of the body (Durham and Wolfe, 1962). The

amount of pesticide collected on each pad

was used to extrapolate to various parts of

the body. The method can also be used to

estimate dermal exposure, by placing the

patches inside the workers PPE. Although

this method is relatively easy to use in prac-

tice, attaching 100 cm

2

pads to the outside

of workers normal PPE, it has been criticised

for providing inaccurate values for poten-

tial dermal exposure (Machera

et al.

1998).

Therefore in modern studies it has been

superseded by the whole body dosimetry

method, which uses a coverall as the dermal

sampler, so avoiding the need for extrapola-

tion. Care needs to be taken with this meth-

od, as pesticide deposit can either pene-

trate or be shed by the dosimeter, leading

to underestimates of exposure. Therefore a

useful variation of the whole body dosime-

ter method uses typical work clothing, such

as cotton coveralls, as the sampling media

(Chester, 1993). This technique allows poten-

tial dermal exposure to be estimated by der-

mal dosimetry in addition to allowing bio-

logical monitoring.

Dosimeters can be worn to measure po-

tential dermal exposure, or as internal gar-

ments to measure dermal exposure. In both

cases care needs to be taken in the use of

the data, as pesticide can penetrate through

to the skin, so not retained by the internal

dosimeter, or included in the dermal expo-

sure measurement.

Measuring the pesticide deposits on

hands or the potential dermal exposure of

the hands is complicated. The hands are of-

ten the part of the body most exposed to

pesticides. The use of absorbent gloves (cot-

ton) worn outside any other protection can

give information about the potential hand

exposure. However absorbent gloves will re-

tain more liquid than the hand itself. Absor-

bent gloves worn inside protective gloves

give an indication of dermal exposure, but

this is only relevant for that particular sce-

nario and the type of glove worn. Outer

protective gloves worn more than once of-

ten contain internal pesticide deposit, car-

ried into the inner glove during removal

and donning by the operator, or by pene-

tration through the material. To overcome

this, hand rinse sampling has been used for

monitoring dermal hand exposure. Prior to

the study the hands need to be washed in

the solvent to remove any background con-

taminants present. Data for the recovery of

the pesticide for the handwash technique

is not really available for such studies, and

for this reason the technique has been crit-

icised as underestimating dermal exposure

of the hands.

Inhalation exposure

The inhalation exposure is carried out

using personal air samplers, which sample

the air in the breathing zone of the opera-

tor using a pump and appropriate filter to

allow the airborne concentration to be de-

termined. The breathing rate of the opera-

tor will vary depending on the type of task

being done, generally considered to be 1.7-

3.5 m

3

/h.

Biomonitoring

The amount of pesticide which has been

absorbed by the body is the ultimate mea-

sure of operator exposure, however lack of

pharmacokinetic data makes interpretation

difficult, together with human variability