Pyrethroid-induced paresthesia--a central or local toxic effect?

Differences in Knowledge, Awareness, Practice, and Health Symptoms in Farmers Who Applied Organophosphates and Pyrethroids on Farms

OBJECTIVE

This cross-sectional study aimed to examine farmers' knowledge, awareness, practices regarding pesticide use, and prevalence of health symptoms related to pesticides exposure among farmers who applied organophosphates (OP) and pyrethroids (PY).

METHODS

Data regarding demographic variables and health symptoms pertinent to pesticide use was collected from 67 farmers who applied OP and 50 farmers who applied PY using interviews from January to March 2021.

RESULTS

The farmers who applied OP had lower knowledge, awareness, and prevention practices regarding pesticide use than those who applied PY. After adjustment of covariate variables, the farmers who applied OP had a significantly higher prevalence of respiratory conditions (OR = 8.29 for chest pain, OR = 6.98 for chest tightness, OR = 27.54 for dry throat, and OR = 5.91 for cough), neurological symptoms (OR = 10.62 for fatigue and OR = 6.76 for paresthesia), and neurobehavioral symptoms (OR = 13.84 for poor concentration, OR = 3.75 for short term memory, and OR = 8.99 for insomnia) related to pesticide exposure than those who applied PY.

CONCLUSION

Our findings suggest that OP had a more adverse effect on human health than PY, resulting in a higher prevalence of pesticide-related symptoms. The outcomes of this study have the benefit of providing vital information for all stakeholders with regard to the implementation of safe practices in the utilization of personal protective equipment (PPE) and pesticide use in a health intervention and health promotion program.

Effect of biosal®, deltamethrin and lambda-cyhalothrin on the activity of GOT, GPT and total protein contents in two fodder pests Hermolaus modestus and Hermolaus ocimumi

The assessment of the comparative effect of biosal (phytopesticide), deltamethrin, and lambda-cyhalothrin (pyrethroids) were made against two fodder pests, Hermolaus modestus and Hermolaus ocimumi by filter paper impregnation method. The activity of total protein contents, GPT (glutamic-pyruvic transaminase) and GOT (glutamic oxaloacetate transaminase) were affected in Hermolaus modestus and Hermolaus ocimumi against biosal, deltamethrin, and lambda cyhalothrin. The activity of total protein contents in H. modestus was 31.053%, 4.607%, and 24.575%, against biosal, deltamethrin, and lambda-cyhalothrin, respectively. The activity of total protein contents was observed as 24.202%, 15.25%, and 56.036% against deltamethrin, lambda-cyhalothrin, and biosal, respectively in H. ocimumi. The activity of GOT was observed as 98.675% for biosal 33.95% for deltamethrin and 83.619% for lambda-cyhalothrin in H. modestus. The GOT activity was estimated in H. ocimumi as 78.831%, 47.645%, and 71.287% against biosal, deltamethrin, and lambda-cyhalothrin, respectively. The efficacy of GPT enzyme against biosal, deltamethrin, and lambda-cyhalothrin was calculated as 89.26%, 73.07%, and 47.58%, respectively in H. modestus. The H. ocimumi showed GPT activity as 77.58% for biosal, 68.84% for deltamethrin, and 52.67% for lambda-cyhalothrin, respectively.

Comparison of phenothrin mousse, phenothrin lotion, and wet-combing for treatment of head louse infestation in the UK: a pragmatic randomised, controlled, assessor blind trial

In this investigation of effectiveness of an alternative pediculicide dosage form, we recruited 228 children and 50 adult participants from Bedfordshire, UK, to a randomised, controlled, assessor blind trial comparing two insecticide products with mechanical removal of lice as a control group.  Participants using insecticide were treated with either the investigative 0.5% phenothrin mousse, for 30 minutes, or 0.2% phenothrin lotion, for 2 hours as the reference product.  Both treatments were applied only once, followed by shampoo washing.  Those treated by wet-combing with conditioner were combed 4 times over 12 days.  Parents/carers carried out the treatments to mimic normal consumer use.  The outcome measure was the absence of lice, 14 days after treatment for the insecticides, and up to 14 days after completion of combing.  Intention to treat analysis of the outcomes for 275 participants showed success for phenothrin mousse in 21/105 (20.0%), in 23/107 (21.5%) for phenothrin lotion, and in 12/63 (19.1%) for wet-combing.  People receiving mousse were 1.07 (95% CI, 0.63 to 1.81) times more likely to still have lice after treatment compared with those treated with lotion. The group of participants who received the wet combing treatment were 1.13 (95% CI, 0.61 to 2.11) times more likely to still have lice after the treatment.  None of the treatments was significantly (p < 0.05) more effective than any other. This study was carried out in an area where moderate resistance to phenothrin was demonstrated after the study by using a bioassay.  Analysis of post treatment assessments found that failure of insecticides to kill louse eggs had influenced the outcome.

Characteristics and magnitude of acute pesticide-related illnesses and injuries associated with pyrethrin and pyrethroid exposures--11 states, 2000-2008

BACKGROUND

Excluding disinfectants, pyrethrins and pyrethroids are the pesticides used most commonly in and around homes. Respiratory effects and paresthesia are among the concerns about pyrethrin/pyrethroid exposures.

METHODS

Acute pesticide-related illness/injury cases were identified from the Sentinel Event Notification System for Occupational Risks-Pesticides Program and the California Department of Pesticide Regulation from 2000-2008. Characteristics and incidence rates were determined for acute pyrethrin/pyrethroid-related illness/injury cases. Logistic regression analyses were performed to determine odds of respiratory and dermal symptoms in persons with illness/injury following pyrethrin/pyrethroid exposure compared to persons with illness/injury following exposure to other pesticides.

RESULTS

A total of 4,974 cases of acute pyrethrin/pyrethroid-related illness were identified. Incidence rates increased over time, reaching 8 cases/million population in 2008. The majority of cases were low severity (85%) and 34% were work-related. Respiratory effects were the most common symptoms reported (48%). Risk of acute respiratory effects were significantly elevated among persons exposed only to pyrethrins (adjusted odds ratio [aOR] 1.79; 95% confidence interval [95% CI]: 1.49-2.16), only to pyrethroids (aOR 1.99 95% CI: 1.77-2.24), to a mixture of pyrethroids (aOR 2.36; 95% CI: 1.99-2.81) or to a mixture containing both pyrethrins and pyrethroids (aOR 2.99; 95% CI: 2.33-3.84) compared to those with illness arising from exposure to other pesticides. The most common factors contributing to pyrethrin/pyrethroid-related illness included exposure from spills/splashes, improper storage, and failure to evacuate during pesticide application.

CONCLUSIONS

The magnitude of acute pyrethrin/pyrethroid-related illness/injury is relatively low but is increasing. As such, additional measures to prevent them are needed.

Pesticide exposure in children

Pesticides are a collective term for a wide array of chemicals intended to kill unwanted insects, plants, molds, and rodents. Food, water, and treatment in the home, yard, and school are all potential sources of children's exposure. Exposures to pesticides may be overt or subacute, and effects range from acute to chronic toxicity. In 2008, pesticides were the ninth most common substance reported to poison control centers, and approximately 45% of all reports of pesticide poisoning were for children. Organophosphate and carbamate poisoning are perhaps the most widely known acute poisoning syndromes, can be diagnosed by depressed red blood cell cholinesterase levels, and have available antidotal therapy. However, numerous other pesticides that may cause acute toxicity, such as pyrethroid and neonicotinoid insecticides, herbicides, fungicides, and rodenticides, also have specific toxic effects; recognition of these effects may help identify acute exposures. Evidence is increasingly emerging about chronic health implications from both acute and chronic exposure. A growing body of epidemiological evidence demonstrates associations between parental use of pesticides, particularly insecticides, with acute lymphocytic leukemia and brain tumors. Prenatal, household, and occupational exposures (maternal and paternal) appear to be the largest risks. Prospective cohort studies link early-life exposure to organophosphates and organochlorine pesticides (primarily DDT) with adverse effects on neurodevelopment and behavior. Among the findings associated with increased pesticide levels are poorer mental development by using the Bayley index and increased scores on measures assessing pervasive developmental disorder, inattention, and attention-deficit/hyperactivity disorder. Related animal toxicology studies provide supportive biological plausibility for these findings. Additional data suggest that there may also be an association between parental pesticide use and adverse birth outcomes including physical birth defects, low birth weight, and fetal death, although the data are less robust than for cancer and neurodevelopmental effects. Children's exposures to pesticides should be limited as much as possible.

Clinical Toxicology of Insecticides

Some insects compete for our food, some damage construction materials and some are important disease vectors in humans and animals. Hence, it is not surprising that chemicals (insecticides) have been developed that kill insects and other arthropods. More recently introduced insecticides, such as the neonicotinoids, have been produced with the intent that humans and animals will not be harmed by their appropriate use. This chapter reviews the clinical features and management of exposure to organophosphorus (OP) and carbamate insecticides, neonicotinoids, phosphides and pyrethroids. In the developing world where the ambient temperature is often high and personal protection equipment often not worn, poisoning particularly from OP and carbamate insecticides is common in an occupational setting, though more severe cases are due to deliberate ingestion of these pesticides. Both of these insecticides produce the cholinergic syndrome. The neonicotinoids, a major new class of insecticide, were introduced on the basis that they were highly specific for subtypes of nicotinic receptors that occur only in insect tissues. However, deliberate ingestion of substantial amounts of a neonicotinoid has resulted in features similar to those found in nicotine (and OP and carbamate) poisoning, though the solvent in some formulations may have contributed to their toxicity. Phosphides interact with moisture in air (or with water or acid) to liberate phosphine, which is the active pesticide. Inhalation of phosphine, however, is a much less frequent cause of human poisoning than ingestion of a metal phosphide, though the toxicity by the oral route is also due to phosphine liberated by contact of the phosphide with gut fluids. It is then absorbed through the alimentary mucosa and distributed to tissues where it depresses mitochondrial respiration by inhibiting cytochrome c oxidase and other enzymes. Dermal exposure to pyrethroids may result in paraesthesiae, but systemic toxicity usually only occurs after ingestion, when irritation of the gastrointestinal tract and CNS toxicity, predominantly coma and convulsions, result.

A pilot study of workplace dermal exposures to cypermethrin at a chemical manufacturing plant

Exposure during the manufacture of pesticides is of particular concern due to their toxicity and because little is known about worker exposure, since most studies have focused on end-use application within agriculture or buildings. Even though dermal exposure can be expected to dominate for pesticides, little is known about workplace dermal exposures or even appropriate methods for their assessment. The current study begins to address this gap by evaluating alternative methods for assessing dermal exposure at a chemical manufacturing plant. For this pilot study, eight workers were recruited from a U.S. plant that produced the pesticide cypermethrin. Exposure was evaluated using three approaches: (1) survey assessment (questionnaire), (2) biological monitoring, and (3) workplace environmental sampling including ancillary measurements of glove contamination (interior and exterior). In each case, cypermethrin was quantified by enzyme-linked immunosorbent assay (ELISA). Environmental measurements identified two potential pathways of cypermethrin exposure: glove and surface contamination. Workplace exposure was also indicated by urine levels (specific gravity adjusted) of the parent compound, which ranged from 35 to 253 μg/L (median of 121 μg/L) with no clear trend in levels from pre- to post-shift. An exploratory analysis intended to guide future studies revealed a positive predictive association (Spearman correlation, p ≤ 0.10) between post-shift urine concentrations and a subset of survey questions evaluating worker knowledge, attitudes, and perceptions (KAP) of workplace dermal hazards, i.e., personal protective equipment self-efficacy, and inverse associations with behavior belief and information belief scales. These findings are valuable in demonstrating a variety of dermal exposure methods (i.e., behavioral attributes, external contamination, and biomarker) showing feasibility and providing measurement ranges and preliminary associations to support future and more complete assessments. Although these pilot data are useful for supporting design and sample size considerations for larger exposure and health studies, there is a need for validation studies of the ELISA assay for quantification of cypermethrin and its metabolites in urine.

Topical absorption and systemic toxicity

Dermal absorption of some chemicals and drugs can cause systemic toxicity. We evaluated several case reports from the past decade, which discuss the dermal absorption of a specific chemical and potential local and systemic effects. We focused on herbicide and pesticide exposure along with exposure to cutaneous medication, occupational contact, and cosmeceutical exposure. Although causality cannot be established in most cases, it is critical to be aware of the possible effects of topical absorption that may not be immediately apparent. We recommended further studies on specific chemicals to ascertain causality and determine the highest exposure level with no observed adverse affect level (NOAEL) and the reference dose (RfD). Post-marketing epidemiology data in most geographical areas are markedly limited. A weak link in public health resides in the inadequate reporting and workup of alleged chemically related adverse effects. This arena mandates a re-thinking of how to increase this reporting, and workup, as a backup to our preclinical and clinical studies. Public awareness and funding will be rewarded by increased evidence to backup pre-approval pre-marketing studies.

Pyrethrin and pyrethroid illnesses in the Pacific northwest: a five-year review

OBJECTIVE

Pyrethrin and pyrethroid insecticides are commonly applied in homes and businesses and on some agricultural crops. This research used a two-state regional approach to analyze reports of acute pesticide poisonings due to pyrethrin and pyrethroid insecticides.

METHODS

The Washington State Department of Health and the Oregon Public Health Division collected pesticide poisoning surveillance data from 2001 through 2005. Cases were included if they involved exposure to at least one pyrethrin or pyrethroid insecticide. Descriptive statistics were calculated; differences between categories were assessed using Chi-square analysis.

RESULTS

A total of 407 cases fit our definition. Overall, the rate of poisoning in Oregon was significantly higher than in Washington (incidence rate ratio 1.70, 95% confidence interval 1.40, 2.07), and rates for both states generally increased during the time period. For both states, most exposures resulted in low severity illnesses (92%), and most were classified as possible cases (73%). Only about one-fourth of cases were related to a person's work. The most common category of clinical signs and symptoms of illness was respiratory (52% of cases), followed by neurological (40% of cases). Exposure route was predominantly inhalation; there was no association between route and case severity. There was a significant association between illness severity and losing time from work or regular activities (p<0.0001).

CONCLUSIONS

Although the majority of pyrethrin and pyrethroid poisoning cases were low in severity, adverse reactions have occurred, as transpired in Oregon in 2005. Regional analysis has the potential to improve the surveillance system and provide unique opportunities for targeting preventive interventions.

Pyrethroid Insecticides: Advances and Challenges in Biomonitoring

Pyrethroid insecticides have a wide variety of applications throughout the world. They are structurally diverse chemicals that are synthetically derived from naturally occurring pyrethrin insecticides. Significant advances in analytical chemistry have led to the development of biomarkers of exposure to pyrethroids, and these methods are currently being applied to study exposure in the general population. This article reviews the chemistry and toxicology of pyrethroid insecticides, with an emphasis on the development of biomarkers to assess environmental exposure. Future challenges in the application of these biomarkers in epidemiological studies are explored, as is a need for improved understanding of the toxicokinetics of pyrethroids in humans.

Biological monitoring of exposure to pyrethrins and pyrethroids in a metropolitan population of the Province of Quebec, Canada

Pyrethroid and pyrethrins are neurotoxic insecticides widely used to control agricultural and domestic insect pests. The general population is potentially chronically exposed through food consumption, but the actual exposure is poorly documented in Canada. This study aimed at obtaining an indication of the absorption of those insecticides in residents of Montreal Island, the largest metropolitan area of the Province of Quebec, Canada. We randomly recruited 120 adults and 120 children aged 18-64 and 6-12 years old, of which 81 adults and 89 children completed the study. The absorption of pyrethroids and pyrethrins was assessed through measurements of six urinary metabolites: chrysanthemum dicarboxylic acid (CDCA), cis- and trans-2,2-(dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acids (cDCCA and tDCCA), cis-2,2-(dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (DBCA), 3-phenoxybenzoic acid (PBA) and 4-fluoro-3-phenoxybenzoic acid (FPBA). Metabolites were determined in 12-h urine collections for children and 2-consecutive 12-h collections for adults, and were analyzed by gas-chromatography/mass spectrometry. In both adults and children, the relative distribution of the various metabolites was as follows: tDCCA>PBA>cDCCA>CDCA>DBCA>FPBA. In adults, median (95th percentiles) cumulative amounts of these metabolites were 12.0 (231.1), 8.2 (177.9), 5.0 (110.1), 0.3 (8.2), 0.1 (4.7) and 0.1 (0.5)pmol/kg bw, respectively, in nighttime 12-h urine collections. Corresponding values in children were 12.6 (207.7), 10.2 (73.2), 5.1 (59.6), 2.1 (14.2), 0.1 (4.9) and 0.1 (0.8)pmol/kg bw. The main metabolites observed are indicative of exposure mainly to permethrin and cypermethrin and amounts absorbed are in the same range in adults and children. The distribution levels of the main metabolites in our sample also appeared similar to those reported in the US population.

A reassessment of the neurotoxicity of pyrethroid insecticides

The pyrethroids are a widely used class of insecticides to which there is significant human exposure. They are however generally regarded as safe to man, and there have been few reports of human fatalities. Their acute toxicity is dominated by pharmacological actions upon the central nervous system (CNS), predominantly mediated by prolongation of the kinetics of voltage-gated sodium channels, although other mechanisms operate. This review summarizes our present understanding of such actions and the pharmacological options to antagonize them. One significant problem is the very clear heterogeneity of pyrethroid sensitivity that is seen across sodium channel subtypes; however, the distribution and function of these across the central nervous system are poorly characterized. The review also provides an overview of recent studies that suggest additional effects of pyrethroids: developmental neurotoxicity, the production of neuronal death, and action mediated via pyrethroid metabolites. The evidence for these is at present equivocal, but all 3 carry important implications for human health.

Oestradiol potentiates the effects of certain pyrethroid compounds in the MCF7 human breast carcinoma cell line

Pyrethroids are the most widely used insecticides for indoor pest control, so human exposure to them is common. The main target of pyrethroids is the nervous system, but their endocrine disrupting capabilities may also be of toxicological concern. In the present study, the proliferation of the breast cancer cell line, MCF7, was studied after a 7-day exposure to various concentrations of pyrethrin, permethrin and cypermethrin. The effects of oestradiol and the combined effects of oestradiol (0.10 nM) and pyrethroids (0.1-100 microM) on MCF7 cell proliferation were also evaluated. Proliferation and cell toxicity were studied by measuring the ATP content with a luminescence method, and mitochondrial metabolic enzyme activity with the WST-1 test. In the ATP test, low concentrations (0.1-1 microM) of pyrethroids in co-exposure with oestradiol caused a clear statistically significant increase in the proliferation of MCF7 cells. This was evident when compared to the proliferative effect caused by 0.1 nM oestradiol alone. High concentrations were cytotoxic, and the greatest cell toxicity was that of cypermethrin, which has a cyano group in its molecular structure.

Poisoning due to Pyrethroids

The first pyrethroid pesticide, allethrin, was identified in 1949. Allethrin and other pyrethroids with a basic cyclopropane carboxylic ester structure are type I pyrethroids. The insecticidal activity of these synthetic pyrethroids was enhanced further by the addition of a cyano group to give alpha-cyano (type II) pyrethroids, such as cypermethrin. The finding of insecticidal activity in a group of phenylacetic 3-phenoxybenzyl esters, which lacked the cyclopropane ring but contained the alpha-cyano group (and hence were type II pyrethroids) led to the development of fenvalerate and related compounds. All pyrethroids can exist as at least four stereoisomers, each with different biological activities. They are marketed as racemic mixtures or as single isomers. In commercial formulations, the activity of pyrethroids is usually enhanced by the addition of a synergist such as piperonyl butoxide, which inhibits metabolic degradation of the active ingredient. Pyrethroids are used widely as insecticides both in the home and commercially, and in medicine for the topical treatment of scabies and headlice. In tropical countries mosquito nets are commonly soaked in solutions of deltamethrin as part of antimalarial strategies. Pyrethroids are some 2250 times more toxic to insects than mammals because insects have increased sodium channel sensitivity, smaller body size and lower body temperature. In addition, mammals are protected by poor dermal absorption and rapid metabolism to non-toxic metabolites. The mechanisms by which pyrethroids alone are toxic are complex and become more complicated when they are co-formulated with either piperonyl butoxide or an organophosphorus insecticide, or both, as these compounds inhibit pyrethroid metabolism. The main effects of pyrethroids are on sodium and chloride channels. Pyrethroids modify the gating characteristics of voltage-sensitive sodium channels to delay their closure. A protracted sodium influx (referred to as a sodium 'tail current') ensues which, if it is sufficiently large and/or long, lowers the action potential threshold and causes repetitive firing; this may be the mechanism causing paraesthesiae. At high pyrethroid concentrations, the sodium tail current may be sufficiently great to prevent further action potential generation and 'conduction block' ensues. Only low pyrethroid concentrations are necessary to modify sensory neurone function. Type II pyrethroids also decrease chloride currents through voltage-dependent chloride channels and this action probably contributes the most to the features of poisoning with type II pyrethroids. At relatively high concentrations, pyrethroids can also act on GABA-gated chloride channels, which may be responsible for the seizures seen with severe type II poisoning. Despite their extensive world-wide use, there are relatively few reports of human pyrethroid poisoning. Less than ten deaths have been reported from ingestion or following occupational exposure. Occupationally, the main route of pyrethroid absorption is through the skin. Inhalation is much less important but increases when pyrethroids are used in confined spaces. The main adverse effect of dermal exposure is paraesthesiae, presumably due to hyperactivity of cutaneous sensory nerve fibres. The face is affected most commonly and the paraesthesiae are exacerbated by sensory stimulation such as heat, sunlight, scratching, sweating or the application of water. Pyrethroid ingestion gives rise within minutes to a sore throat, nausea, vomiting and abdominal pain. There may be mouth ulceration, increased secretions and/or dysphagia. Systemic effects occur 4-48 hours after exposure. Dizziness, headache and fatigue are common, and palpitations, chest tightness and blurred vision less frequent. Coma and convulsions are the principal life-threatening features. Most patients recover within 6 days, although there were seven fatalities among 573 cases in one series and one among 48 cases in another. Management is supportive. As paraesthesiae usually resolve in 12-24 hours, specific treatment is not generally required, although topical application of dl-alpha tocopherol acetate (vitamin E) may reduce their severity.

The toxicity of pyrethroid compounds in neural cell cultures studied with total ATP, mitochondrial enzyme activity and microscopic photographing

Pyrethroids are important insecticides used largely because of their high activity as an insecticide and their low mammalian toxicity. Some studies have demonstrated that these products, especially compounds with an α-cyano group, show neurotoxic effects on the mammalian central nervous system (CNS). In this study, we investigate with different methods the cell toxic effects of commercial, chemically different pyrethroid compounds on neuronal cell line SH-SY5Y. Natural pyrethrin and permethrin (both with no α-cyano group) and cypermethrin (with an α-cyano group), were studied. For toxicity determinations, SH-SY5Y neuroblastoma cells were exposed to pyrethroids at 0.1-100μM concentrations for 1 day. The cell toxicity was evaluated by determining the total ATP with a luminescence method, the mitochondrial metabolic activity (WST-test) with a photometric method, and the morphological changes of the cell cultures with microscopic digital photographing at different dose levels of compounds. The results obtained with WST-1 method and with the measurement of total ATP were different. ATP measurement seemed to show cytotoxicity at lower concentrations than WST-1 method. There was induction of enzyme activities with WST-1 test with all pyrethroid compounds studied at low concentrations. With the ATP assay, exposure to 0.1-100μM of natural pyrethrin, as well as of permethrin and cypermethrin showed dose-dependent cytotoxicity. The most toxic pyrethroid was cypermethrin followed by permethrin and natural pyrethrin. Our study confirms that the cell toxicity was dependent on the chemical structure of pyrethroids and pyrethroids without an α-cyano group show the weakest physiological effect. Microscopic photographs of exposed cell cultures correlated to the toxic effects revealed by the metabolic tests.

Biological monitoring of workers after the application of insecticidal pyrethroids

OBJECTIVES

Pyrethroids are applied as insecticides throughout the world. Human metabolism of pyrethroids results in urinary metabolites that are suitable for biological monitoring. The aim of the study was to evaluate individual exposure due to occupational application of pyrethroids as a precondition for the assessment of health risks.

METHODS

Thirty-six workers who applied insecticides and other pesticides in Germany collected samples of their urine (24 h) after having used various pyrethroids (alpha-cypermethrin, cypermethrin, cyfluthrin, deltamethrin, tau-fluvalinate, permethrin, lambda-cyhalothrin) in agriculture, greenhouses or indoor pest control. Biological monitoring was carried out and metabolites were analysed in 61 urine samples by GC-MS: cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid ( cis-Cl(2)CA and trans-Cl(2)CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid ( cis-Br(2)CA), 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (FPBA). Forty-five urine specimens collected (24 h) from persons with no occupational exposure to pyrethroids served as controls. Concentrations were related to creatinine content and expressed as microgrammes per gramme creatinine.

RESULTS

Control urine samples revealed a considerable background excretion of pyrethroid metabolites by the general population. The 95th percentile of the concentrations of Cl(2)CA and cis-Br(2)CA were 2.1 and 0.1 microg/g creatinine, respectively. FPBA was not detected in any control urine and was found in only one sample within the complete study. After occupational application of pyrethroids the highest concentrations of metabolites in urine samples were detected within the group of indoor pest-control operators. The maximum concentrations (median values) of Cl(2)CA, 3-PBA, and cis-Br(2)CA were 92.4 microg/g (1.8 microg/g), 57.5 microg/g (1.4 microg/g) and 1.1 microg/g (median below detection limit), respectively. Workers in greenhouses excreted metabolites with median concentrations as follows: 2.9 microg/g Cl(2)CA, 0.5 microg/g cis-Br(2)CA and 2.9 microg/g 3-PBA. Medians of the metabolite concentrations in specimens from agricultural workers were below the detection limit with regard to Cl(2)CA and cis-Br(2)CA, but the value was 0.6 microg/g for 3-PBA. Pest-control operators excreted significantly higher concentrations of Cl(2)CA and 3-PBA than workers in agriculture on a collective basis. Comparison of the excreted concentrations of metabolites with values of acceptable daily intake (ADI) of pyrethroids set by WHO revealed that the amount of pyrethroids that had been taken up during occupational application was not considerably higher than the ADI.

CONCLUSIONS

As a consequence, we conclude that adverse health effects are not to be expected after workers' occupational exposure to pyrethroids in Germany, provided that the application is carried out properly. Good working practices need to be supported by adequate supervision with regard to occupational hygiene and medicine.