K Xuyen, MD, PhD, National Institute of Occupational and Environmental Health, Hanoi, Vietnam (Corresponding Author)
PC Hoi, Ministry of Agriculture and Rural Development, Hanoi, Vietnam
PQ Trung, Ministry of Agriculture and Rural Development, Hanoi, Vietnam

Generalities
Vietnam is an agricultural country, so pesticide is used more and more for the prevention of insects and increase of rice productivity as well as other industrial trees, such as rubber, coffee and tea.

According to the investigations of the agricultural and health branch, at present, the pesticides mostly used in Vietnam are organophosphates and carbamates (85-96.8%). The cultivation area using pesticides in the 1960's was only 0.5% with the quantity under 100 tonnes yearly, but it increased up to 50% with 10000 tonnes a year in the 1980's, and in the early 1990's, the cultivation area grew to 90% and pesticide use increased to 20000 tonnes yearly.

Because of broad pesticide use, Vietnam rice productivity increased from 10 million tonnes yearly in the 1970's up to 30 million tonnes yearly, and Vietnam has become one of the biggest rice exporters in the world.

Besides the great effects of pesticide use, the hazard of environmental pollution and the number of pesticide poisonings are increasing more and more. This problem requires much attention.

The objectives of the research work are as follows:
1- Investigation of the working environment and the health of workers exposed to pesticides.
2- Evaluate the relationship between working environment and farmers' health, especially the occupational skin diseases of pesticide-exposed subjects.

Methods and materials
1- Subjects:

Results

Table 1. The situation of pesticides use:

Table 2. Wofatox concentration in the air:

Table 3. The major signs and symptoms:

Table 5. Comparison of dermatosis between groups directly and indirectly exposed to pesticides:

Table 6. Patch test (n=138):
138 subjects sensitive to pesticides were submitted to patch testing; the positive reaction was 39.73%

Discussion
- At present, the pesticides mostly used in Vietnam are organophosphates and carbamates (85-96.8%). The quantity of pesticides used by family tea farms was more than by government tea farms.
- The concentration of wofatox was 6-10 times higher than Maximum Allowable Concentration
- Almost all spraymen had such symptoms as prurigo (58.26 %), headache (44.44 %), fatigue (36.58 %) and nausea (15.17 %).
- Work-related disease such as melanosis was 8.94 % and allergic contact dermatitis in the pesticide-exposed group was 16 times higher than in the non-exposed group and the difference between rates of diseases was statistically significant (p < 0.001, OR = 16.06, 95% CI = 8.32-31.64).
- 138 subjects sensitive to pesticide were tested; the patch test positive reaction was 39.73 %, and the strong reaction was 8.70 % (Padan). It showed the cause of occupational skin diseases of pesticide subjects in tea farms in Vietnam.

Conclusions
- Up to now in Vietnam, the most frequently used pesticides are organophosphates and carbamates.
- The skin disease rate of the subjects exposed to pesticide was very high (73 %). The work-related disease such as allergic contact dermatitis in the pesticide-exposed group was 16 times higher than in the non-exposed group. It showed the cause and effect relationship between the working environment and occupational skin diseases.

Recommendations
- To promote education on the safe use of pesticides on government and family tea farms.
- The contacters' health needed proper concern and good protection.

References

1/ Nguyen duy Bao, Nguyen huy Dan, Bui van Chung et al ., Evaluation of the air pollution and health impacts due to the use of pesticides in agriculture, The 2nd National Scientific Conference on Occupational health , 13-15 December 1995, Hanoi, Vietnam.

2/ Tran huy Tho, The pesticides using in Tea farm branch. National wokshop on impact of pesticides on Human heath in Viet nam, Hanoi, 27-28 April 1994 .

3/ Nguyen thi hong Tu et al., Workshop on safe use of Pesticides, Hanoi, 29-30 August 1997.

4/ Le Trung et al., Workshop on the safe use of pesticides and on the dianosis and treatment of pesticide poisoning, Hanoi, Vietnam, August, 1995.

5/ Khuc Xuyen, Le tu Van, The dermatosis in Agricuture, pp 121 - 128, The Occupational Skin Diseases (Book) Hanoi 1998

6/ Khuc Xuyen, Le tu Van, The skin diseases due to pesticides, PP 129 - 134, The Occupational Skin Diseases (Book), 1998.

7/ Bates, J.A.R., Safe practice in pesticide use, WHO regional office for Europe - Copenhagen 1982, pp 195 - 213.

8/ Coppleston, J-F et al., Expose to pesticides in agriculture - A survey of spraymen using dimethoate in Sudan (1976), Bulletin of the World Health Organization 54, pp 217 - 223.

9/ WHO. The WHO recommended classification of pesticides by hazard and guidelines to classification 1990-1991, Unpublished WHO document WHO/PCS/90-I - 1211 Geneva 27, Switzerland, 1990.

10/ Robert M. Adams, Occupational Skin Disease, pp 136 - 149, Grune & Tratton, Inc., 111 Fifth Avenue, New York, New York 10003, 1983.