Research at Massey University has shown that agricultural workers have the highest incidence of leukaemia of all New Zealand occupation groups. The cause is expected to be exposure to pesticides. The Centre for Public Health Research has just released analysis of a study started in 2003-04, when researchers interviewed 225 cancer patients aged 25-75 and 471 randomly selected participants from the general population. They found elevated leukaemia risk four or five times greater among market gardeners and nursery growers compared to the general population. Market farmers and crop growers, and field crop and vegetable growers, also all experienced varying degrees of elevated risk. Female workers were shown to be at greater risk than males. According to Dr Dave McLean;

It is not clear why this gender difference exists, but it has been hypothesised that it may be due either to the different tasks (and therefore potential for exposure) traditionally performed by men and women in horticultural occupations, or to the fact that some of the chemicals are endocrine disruptors that affect women in a different way than they do men.

Studies done in Italy and the United States showed similar trends. The study also suggested an increased risk of contracting leukaemia for other occupations including electricians, blacksmiths and toolmakers, slaughterers and people working in textile bleaching, dyeing or operating dyeing and with cleaning machines. Occupational cancers account for more than 300 deaths in New Zealand each year, with the National Occupational Health and Safety Advisory Committee estimating that 30 deaths annually from leukaemia are attributable to occupational exposures.
The government has recently made it compulsory for temporary migrant workers in the horticulture and viticulture industries to have health insurance.