Aprea et al. (1994) “Biological monitoring of exposure to organophosphorus insecticides by assay of urinary alkylphosphates: influence of protective

measures during manual operations with treated plants”

Study description:

Aprea et al. studied a population of 12 workers exposed to chlopyrifos-methyl and azinphos-methyl during work (thinning immature peaches) in a previously sprayed peach orchard presumably in Italy. Urine samples were taken on the Monday before work (pre-shift) and over the whole monitoring period (one week). Samples were analyzed for various dialkylphosphates, but only results for dimethylalkylphosphates were reported. In parallel, the active ingredients were analyzed every day in hand wash solution (95% ethanol) collected over one working day.

Workers were divided into four groups based on the type of protection they were wearing:

Group 1: rubber gloves + felt face-mask (2 women)

Group 2: waterproof cotton gloves + felt face-mask (2 women) Group 3: cotton gloves + felt face mask (2 women)

Group 4: Cotton gloves (5 women)

One worker (male) who did not wear any kind of protection apart from his normal clothes was also monitored. It is not described in detail what a “felt face-mask” is and what level of protection was provided by this respiratory protection device.

Based on the comparison of the mean urinary excretion of dimethylalkylphosphates between Groups 1 – 4 respectively and the one worker without any kind of protection, dermal protection factors for the gloves were derived. This was not done by the study authors and only calculated in the context of the present evaluation. For the calculation the pre-shift value calculated for the group was subtracted from the mean value calculated for the group. This was compared to the result obtained for the one person without dermal protection (minus pre-shift value of the whole group).

For group 1, a protection factor of 87.8%, for group 2 a PF of 85.3% and for group 3 a PF of 98.4% was calculated. For these three groups, inhalation exposure was controlled by wearing a felt face-mask. For limitations of these masks please see below. For group 4 a PF of 90.3 % was calculated, but in this group inhalation exposure was not controlled with masks. In addition to the mean values authors also provide the geometric mean (GM) and the median for each group. Using the GM for calculation of protection factors leads to a value of 92 % for group 2 and 99 % for group 3. This shows that calculated protection factors are highly dependent on the initial values.

Limitations of the study:

 The number of datasets is very limited. Only one worker was studied who did not wear any protection and who served to compare with protected workers.

Groups 1 – 4 consisted of two or five workers. This small amount of datasets is reflected in the range of the measured values (e.g. group 3: 47.0 – 1432.0 nmol dimethylalkylphosphates /g creatinine).

 The pre-shift value is averaged for all 12 participants (range 27.6 – 1602.2 nmol/g creatinine). There is a possibility that the worker wearing no protection at all may have higher levels of dimethylalkylphosphates in the pre-shift urine sample. This would also influence the calculation of the protection factors. In general, pre-shift values for exposed individuals were higher by a factor 2 than for a control group (99 individuals not occupationally exposed to organophosphorus insecticides).

 The efficiency of the felt face-masks worn by groups 1 - 3 is not reported and cannot be estimated since the authors do not describe what a felt face-mask is.

Therefore, it has to be assumed that protection from inhalative exposure is not 100%, and exposure may also have resulted from inhalation.

 Based on the study results inhalation seems to be a relevant exposure route.

Absorption via inhalation is less than via dermal exposure. The authors are surprised by this observation because the application of the insecticides was 20 days (chlorpyrifos.methyl) and 7 days (azinphos-methyl) before workers entered the orchard.

 The low exposure of workers in group 3 is surprising since they wear the least efficient protection (cotton gloves). Authors conclude that compliance of workers in the other groups was bad, because rubber gloves and waterproof gloves are not so pleasant to wear and are frequently taken off for brief periods.

 All workers divided over the four groups were women. The one worker not wearing any protection at all was a man. No information on gender differences for the metabolism of chlopyrifos-methyl and azinphos-methyl in the body are reported in the paper. However, it is possible, that these differences exist. In combination with the limited number of subjects this is a major limitation of the study.

Conclusion:

The major limitation of the study by Aprea et al. is the small cohort. Only one individual represents working without any protection equipment and also the other exposure groups consist of only two or five workers. In addition, the efficiency of the felt face-mask is not clear and exposure via inhalation cannot be ruled out. Besides, the compliance of workers to wear dermal protection was not ideal.

6.3 Results

The resulting protection factors from the six biomonitoring studies described in detail in section 6.2 are listed in Table 6.3. Due to the limitations of the studies all of the listed protection factors have to be considered with reservation and an overall conclusion is not possible.

All of the evaluated studies considered the dermal protection by gloves made of different materials. In one case (Wang et al, 2006) barrier cream was also evaluated, Landers and Hinke studied the effect of whole body clothes.

No relevant studies were identified which could be used as a basis for deriving dermal protection factors for coveralls, shoes or aprons explicitly.

Table 6.3 Dermal protection factors derived from biomonitoring studies Study author and year

of publication

gloves Barrier

cream

Whole body clothes

Scheepers et al, 2009 74 % - -

Chang et al, 2007 49% (53.6%)

(methyl hippuric acid) - - 69% (72.4%)

(mandelic acid) - -

Chang et al, 2004 74.76%

(metabolites in urine) - - 68.9 %

(metabolites in plasma) - -

Wang et al, 2006 49 % 40 % -

Landers and Hinke,

1992 7.69 % - 100 %

Aprea et al 1992 87.8 %

(rubber gloves) - -

85.3 %

(waterproofed cotton gloves) - - 98.4 %

(cotton gloves) - -

90.3 %

(cotton gloves, no control of inhalation exposure)

- -

6.4 Discussion

6.4.1 Requirements for a good biomonitoring study which can be used to