The catalytic efficiency with which PON1 can degrade toxic OPs determines the degree of protection that PON1 can provide for organism. The higher the concentration of PON1 the better the protection provided. PON1 activity is much lower in neonates, so neonates are more sensitive to OP exposure. In 2006, reports up to a 13-fold variation was seen in PON1 levels in adults, as well as, specifically regarding sensitivity to diazoxon, a variation up to 26 and 14-fold was reported in a group of newborns and Latino mothers. This wide range in variability of enzyme levels determining a humans sensitivity to various OPs is being researched further. Diagnosis
A number of measurements exist to assess exposure and early biological effects for organophosphate poisoning. Measurements of OP metabolites in both the blood and urine can be used to determine if a person has been exposed to organophosphates. Specifically in the blood, metabolites of cholinesterases, such as butyrylcholinesterase (BuChE) activity in plasma, neuropathy target esterase (NTE) in lymphocytes, and of acetylcholinesterase (AChE) activity in red blood cells. Due to both AChE and BuChE being the main targets of organophosphates, their measurement is widely used as an indication of an exposure to an OP. The main restriction on this type of diagnosis is that depending on the OP, the degree to which either AChE or BuChE are inhibited differs; therefore, measure of metabolites in blood and urine do not specify which OP agent is responsible for the poisoning.
Standard treatments for OP poisoning are ineffective for OPIDP. COPIND occurs without cholinergic symptoms and is independent of AChE inhibition. COPIND appears with a delay and is long lasting. Symptoms associated with COPIND include cognitive deficit, mood changes, autonomic dysfunction, peripheral neuropathy, and extrapyramidal symptoms. The underlying mechanisms of COPIND have not been determined, but it is hypothesized that withdrawal of OP pesticides after chronic exposure or acute exposure could be a factor. Pregnancy
Evidence of exposure to OP pesticides during gestation and early postnatal period have been linked to neurodevelopmental effects in animals, specifically rats. Animals exposed in utero to chlorpyrifos exhibited decreased balance, poorer cliff avoidance, decreased locomotion, delays in maze performance, and increased gait abnormalities. Early gestation is believed to be a critical time period for the neurodevelopmental effects of pesticides. OPs affect the cholinergic system of fetuses, so exposure to chlorpyrifos during critical periods of brain development potentially could cause cellular, synaptic, and neurobehavioral abnormalities in animals. In rats exposed to methylparathion, studies found reduced AChE activity in all brain regions and subtle alterations in behaviors such as locomotor activity and impaired cage emergence. Organophosphates as whole have been linked to decreases in the length of limbs, head circumference, and slower rates of postnatal weight gain in mice. Cancer
The International Agency for Research on Cancer (IARC) found that organophosphate exposure may increase cancer risk. Tetrachlorvinphos and parathion were classified as "possibly carcinogenic", malathion, and diazinon. Cause
OP pesticide exposure occurs through inhalation, ingestion and dermal contact.