Australian farmers and their workers are exposed to a wide variety of pesticides [
1]. Pesticides are substances that destroy, repel or attack pests that have a negative effect on productivity and profitability of a farming enterprise. Pesticide groups include herbicides, insecticides, fungicides and rodenticides. Organophosphate (OP) insecticides are widely used for animal husbandry practices (Naphthalophos sheep drench), public health (head lice, locust control), and in crop production (Dimethoate for insect control). The OP class of insecticides effect the nervous system with poisonings most common among agricultural workers and children [
2,
3]. OPs are regularly used as a form of pest control on most farms and farmers have enhanced their understanding of pesticide use and handling. However, many are still not meeting the full range of personal protection standards in their own handling and application [
4]. Routes of human exposure include dermal absorption, inhalation and ingestion [
5]. Symptoms of OP toxicity are caused by inhibition of the enzyme acetylcholinesterase (AChE). Inhibition of AChE results in the subsequent accumulation of acetylcholine at the cholinergic synapses of nerves causing uncontrolled firing of the synapse [
1,
6]. Subclinical effects of chronic OP exposure such as AChE inhibition may be detected early by biological tests. Recovery from AChE depression is prolonged, due to the irreversible binding of OPs to the red blood cell and its subsequent 120 day life cycle [
7]. Monitoring exposure to organophosphates involves the measurement of peripheral cholinesterase enzymes that are inhibited by organophosphates. These include; erythrocyte cholinesterase (EAChE) and serum cholinesterase (SAChE). Organophosphates have been associated with chronic neurological disease such as impaired memory, impaired fine motor skills control and Parkinson’s disease [
8]. The evidence suggests that whilst an acute episode experience may not have occurred, exposure over a long period of time (such as in workers dipping sheep) may result in neurological conditions such as Parkinson’s disease and neuropsychiatric conditions [
6,
8,
9]. The window for exposure to toxicants may occur years before the onset of neurological symptoms [
8,
10,
11], this is particularly important for sheep and crop producers exposed to long-term, low levels of OPs. The Western region of the state of Victoria in Australia has been a centre of sheep production, since settlement, and a large number of farmers have been exposed to OPs through routine sheep dipping (lice control), drenching (control internal parasites), jetting (blow fly control) and spraying of pastures (insect control). The National Centre for Farmer Health (NCFH) is in a unique position to monitor these farmers and workers, and work with farmers to incorporate cholinesterase testing as part of their assessments during peak periods and provide much needed data for them on exposures in this area. Additional practices such as mixing contaminated laundry and storing pesticides in the home are not only common causes of exposure to the farmer and farm worker, but may also be placing other household members at risk, particularly children [
12]. Work completed by the program Sustainable Farm Families™ [
13] has identified that there is strong interest from farm men and women who wish to investigate exposures and possible health impacts of agricultural chemical use.
The acute effect of OP exposure is well documented in Australia and overseas for humans, pests and animals [
3,
6,
9]. However, the extent to which asymptomatic monitoring is taking place is not well known or documented. This research builds on work conducted by the NCFH. It utilises the data collection methods of the Sustainable Farm Families™ which includes health behaviours and conditions, with the expectation that this monitoring EAChE testing will be integrated into this procedure, providing the springboard to break through barriers that are currently inhibiting best practice chemical handling safety in Australia.
Understanding the mode of action of a chemical is a critical component of the risk assessment process. Cholinesterase activity is a direct link to exposure and this pilot study will produce valuable data on possible exposures for farmers routinely using OP’s for animal husbandry or crop production.
Monitoring cholinesterase levels during agricultural health screening and assessment is a key objective of Agrisafe™ clinics in Australia. However, its incorporation into such clinics will depend on health professional’s skills and knowledge. This study will further prepare health care providers for integration of correct cholinesterase testing procedures into point of care (POC) health checks. This work will further highlight pesticide exposure as a risk for farmers, workers and their families, leading to an easily adopted method that will quantify the environmental exposures providing early detection. Research has also shown links between cholinesterase activity and vascular complications in diabetic patients [
14]. Diabetes is a disease also of increasing concern to the farming and rural population in Australia [
15].