Sunscreens can increase dermal penetration of 2,4-dichlorophenoxyacetic acid

Effects on reproductive, biochemical and genotoxic parameters of herbicides 2,4-D and glyphosate in silver catfish (Rhamdia quelen)

The objective of this work was to evaluate the effects of the herbicides 2,4-D, glyphosate and the mixture of both on oxidative stress, genotoxicity and the rates of fertilization, hatching and larval normality in silver catfish. Exposure to glyphosate and the mixture of herbicides significantly decreased the fertilization of oocytes and the hatching of eggs. The different concentrations of 2,4-D and glyphosate, in addition to the mixture of both, did not affect the rates of larval normality, the activity of CAT, GST, LPO, and PCO. SOD activity was not evident in any of the treatments. Exposure to 2,4-D and the mixture of herbicides caused damage to the genetic material of larvae silver catfish. Our results show that although high concentrations of the herbicides were used, changes caused by them were detected in only some of the tested biomarkers.

Effects of active sunscreen ingredient combinations on the topical penetration of the herbicide 2,4-dichlorophenoxyacetic acid

Sunscreen use can reduce the incidence of certain skin cancers. However, a number of commercially available formulations have been shown to enhance the transdermal penetration of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Most of the active ingredients used in these compounds can individually act as penetration enhancers. Commercial sunscreens frequently contain multiple active ingredients in order to provide broad sunscreen protection. The purpose of this study was therefore to examine the effect of these active ingredient combinations on the transdermal absorption of 2,4-D in vitro. All six of the combinations tested resulted in increased cumulative penetration ( P <0.01) and faster lag times ( P <0.05). The 2,4-D cumulative penetration in the presence of the OFF! Deepwoods combination was significantly greater than the absorption with either the individual ingredients or their average ( P <0.05). A systematic study designed to isolate the chemicals responsible for this enhancement demonstrated that with UV absorbers DEET synergistically increased the 2,4-D penetration and that DEET’s cumulative enhancement properties correlate with its concentration. By contrast, octocrylene significantly slowed the lag time when used in combinations and was the only active ingredient that showed any antagonistic effects on 2,4-D penetration. Because none of the active ingredient combinations were able to inhibit dermal uptake of 2,4-D, it seems that proper selection of inert ingredients may be the most feasible solution for reducing penetration enhancement.

Sunscreens containing physical UV blockers can increase transdermal absorption of pesticides

People are encouraged to wear sunscreens because of their effectiveness at reducing the risk of skin cancer. The dermal penetration of the herbicide 2,4-D can be enhanced by commercial formulations containing chemical ultraviolet (UV) absorbers, the absorbers themselves and the insect repellent DEET. This work has been extended to determine whether commercially available sunscreens containing the physical UV absorbers titanium dioxide (TiO2) or zinc oxide (ZnO) enhance the transdermal absorption of pesticides. Hairless mouse skin was pretreated with either commercially available sunscreens or the UV absorbers themselves, dissolved in phenyl trimethicone. In vitro permeability studies were performed with the pesticides 2,4-D, paraquat, parathion or malathion. The data demonstrate that pretreatment with five of the nine sunscreens tested increased the transdermal absorption of 2,4-D ( P <0.05). Transdermal studies using paraquat, parathion and malathion pretreated with a representative sunscreen all demonstrated significant penetration enhancement when compared to controls ( P <0.05). Repeated 2,4-D and sunscreen applications resulted in either no change between pulses or an increase in absorption after the second pulse depending on the washing regimen. Examining penetration of individual UV absorbers formulated in phenyl trimethicone showed that that ZnO can impede 2,4-D penetration and TiO2 had no effect. Combining UV absorbers in the presence of trimethicone resulted in ‘sunscreens’ that could actually inhibit 2,4-D penetration. Inert ingredients therefore control the increased absorption seen in commercial sunscreen products and this enhancement can be eliminated by substituting phenyl trimethicone as the solvent. Sunscreen use must still be encouraged even with the undesirable side effect of increased penetration through the skin.

Assessment of dermal absorption of DEET-containing insect repellent and oxybenzone-containing sunscreen using human urinary metabolites

Mutual enhancement of dermal absorption of N,N-diethyl-m-toluamide (DEET) and oxybenzone (OBZ) has been reported recently with DEET and OBZ being active ingredients of insect repellent and sunscreen, respectively. To assess the reported enhancing effect directly, we used human urinary metabolites as biomarkers; besides, we also sought to determine the best way for concurrent use of these two products without extra absorption of either. Four dermal application methods were used: DEET only (S1), OBZ only (S2), DEET on top of OBZ (S3), and OBZ on top of DEET (S4). Among the study methods, there was a significant difference (p = 0.013), which was attributed to the difference between S1 and S4, suggesting that applying OBZ over DEET on the skin lead to significantly higher absorption of DEET. Using both products in reverse order, (S3) did not result in extra DEET absorption significantly. As for OBZ permeation, no significant difference was observed among the methods. In summary, the enhancement of DEET absorption is confirmed for OBZ being applied over DEET on the skin; should concurrent use of both be necessary, applying sunscreen (OBZ) first and then insect repellent (DEET) with a 15-min interval is recommended.

Sun lotion chemicals as endocrine disruptors

Ultraviolet solar radiation is a well-known environmental health risk factor and the use of sun lotions is encouraged to achieve protection mainly from skin cancer. Sun lotions are cosmetic commercial products that combine active and inactive ingredients and many of these are associated with health problems, including allergic reactions and endocrine disorders. This review focuses on their ability to cause endocrine and reproductive impairments, with emphasis laid on the active ingredients (common and less common UV filters). In vitro and in vivo studies have demonstrated their ability to show oestrogenic/anti-oestrogenic and androgenic/anti-androgenic activity. Many ingredients affect the oestrous cycle, spermatogenesis, sexual behaviour, fertility and other reproductive parameters in experimental animals. Their presence in aquatic environments may reveal a new emerging environmental hazard.

Metabolism of UV-filter benzophenone-3 by rat and human liver microsomes and its effect on endocrine-disrupting activity

Benzophenone-3 (2-hydroxy-4-methoxybenzophenone; BP-3) is widely used as sunscreen for protection of human skin and hair from damage by ultraviolet (UV) radiation. In this study, we examined the metabolism of BP-3 by rat and human liver microsomes, and the estrogenic and anti-androgenic activities of the metabolites. When BP-3 was incubated with rat liver microsomes in the presence of NADPH, 2,4,5-trihydroxybenzophenone (2,4,5-triOH BP) and 3-hydroxylated BP-3 (3-OH BP-3) were newly identified as metabolites, together with previously detected metabolites 5-hydroxylated BP-3 (5-OH BP-3), a 4-desmethylated metabolite (2,4-diOH BP) and 2,3,4-trihydroxybenzophenone (2,3,4-triOH BP). In studies with recombinant rat cytochrome P450, 3-OH BP-3 and 2,4,5-triOH BP were mainly formed by CYP1A1. BP-3 was also metabolized by human liver microsomes and CYP isoforms. In estrogen reporter (ER) assays using estrogen-responsive CHO cells, 2,4-diOH BP exhibited stronger estrogenic activity, 2,3,4-triOH BP exhibited similar activity, and 5-OH BP-3, 2,4,5-triOH BP and 3-OH BP-3 showed lower activity as compared to BP-3. Structural requirements for activity were investigated in a series of 14 BP-3 derivatives. When BP-3 was incubated with liver microsomes from untreated rats or phenobarbital-, 3-methylcholanthrene-, or acetone-treated rats in the presence of NADPH, estrogenic activity was increased. However, liver microsomes from dexamethasone-treated rats showed decreased estrogenic activity due to formation of inactive 5-OH BP-3 and reduced formation of active 2,4-diOH BP. Anti-androgenic activity of BP-3 was decreased after incubation with liver microsomes.

Chlorine and hydrogen cyanide gas interactions with human skin: in vitro studies to inform skin permeation and decontamination in HAZMAT incidents

Accidental or intentional toxic gas releases may result in significant public health and psychological consequences. Management of exposed individuals during HAZMAT incidents should be risk-based and supported by a suitable scientific evidence base. There appear to be large evidence gaps in relation to dermal absorption of gases, as well as management advice for potentially exposed individuals. Chlorine and hydrogen cyanide are two common HAZMAT gases and this paper addresses the need for experimental data tailored to HAZMAT scenarios and first responders. In addition to time variations of gas concentration, the modifying effects of clothing, temperature, and oil-based sunscreen on epidermal absorption and penetration are assessed. Results for chlorine show little penetration up to 500 ppm but with small enhancing effects due to heavy cotton and oil-based sunscreen. Hydrogen cyanide up to 800 ppm shows minor penetration consistent with previous studies, with little variability in the presence of sunscreen and clothing. Practical guidelines to support the decision-making of emergency responders with regard to personal decontamination have been derived.

Application of skin contamination studies of ammonia gas for management of hazardous material incidents

In an atmospheric HAZMAT release unprotected public dermal exposure is often of short duration, but with potential secondary exposure if not decontaminated promptly. Mass decontamination is resource intensive and needs to be justified. For many HAZMAT agents there is no evidence-base on which to provide guidance on decontamination, particularly for non-symptomatic worried well. It is important to understand the influence of street clothing and environmental and other factors. Ammonia is a common HAZMAT agent and was selected for in vitro human skin studies of absorption, penetration and off-gassing at test concentrations up to 2000 ppm, incorporating primary and secondary exposure combinations up to 60 min. Intact skin provided a good barrier to ammonia penetration. Heavy street clothing such as denim was found to act as an initial barrier to skin absorption but subsequently as a reservoir for secondary exposure, under variable temperature and humidity conditions. Rapid off-gassing was observed for lighter fabrics including polyester and cotton. The findings here have been summarized as a set of practical guidelines for emergency responders who are required to make decisions about ammonia decontamination including for non-symptomatic individuals. This evidence-based diagrammatic approach allows for specific actions based on different atmospheric ammonia concentrations and other parameters.

Bioaccessibility of pesticides and polychlorinated biphenyls from house dust: in-vitro methods and human exposure assessment

Semi-volatile chemicals like pesticides and polychlorinated biphenyls (PCB) tend to accumulate in house dust. This may result in residues of some parts per million (p.p.m.), closely associated with health impairments and diseases like cancer. To explain these associations, we must establish whether a relevant absorption from house dust into human organisms occurs, and most crucially the release of chemicals, that is, their bioaccessibility. Digestive as well as dermal bioaccessibilities were examined using in-vitro methods. On average, the digestive bioaccessibility was ~40% for the pesticides and ~60% for the PCB. The dermal penetration availability reached ~60% for the pesticides and ~70% for the PCB (percentages of the concentrations in the dust). Based on the bioaccessibility, an estimate of internal exposure was calculated and expressed as percentages of acceptable or tolerable daily intake (ADI/TDI) values. Exposure via the respiratory tract proved to be very low. Exposure via the digestive tract had maximum values of 4% for pesticides and 12% for PCB. Dermal exposure was much higher. Even for average concentrations in house dust (≈0.5 p.p.m.), children exposed to DDT and PCB showed up to 300% of the ADI/TDI values, and adults about 60%. With high concentrations of contaminants in house dust, the maximum doses absorbed through the skin reached 5000%.

2,4-Dichlorophenoxyacetic acid effects on nephrotoxicity in rats during late pregnancy and early postnatal periods

2,4-Dichlorophenoxyacetic acid (2,4-D) is largely used as a selective herbicide in Tunisia. The purpose of this study was to investigate the effects of 2,4-D on the kidneys of adult rats and their suckling pups. Female Wistar rats were divided into two groups: the controls and the treated rats that received 600 mg/L of 2,4-D in their drinking water from the 14th day of pregnancy until day 14 after delivery. Exposure to 2,4-D induced nephrotoxicity as evidenced by an increase in thiobarbituric acid reactive substances and protein carbonyl levels and a decrease in antioxidant enzyme activities such as catalase, superoxide dismutase, glutathione peroxidase in the kidneys of suckling pups and their mothers. In addition, a significant decline in kidney glutathione, non-protein thiol and vitamin C levels was also observed. Histological changes, seen in the kidney of mothers and their pups treated with 2,4-D are characterized by a narrowed Bowman's space, tubular epithelial cells degeneration, widened tubular lumen and vascular congestion.

Moisturizing Lotions can Increase Transdermal Absorption of the Herbicide 2,4-Dichlorophenoxacetic Acid Across Hairless Mouse Skin

Moisturizing lotions can be an effective treatment for occupationally induced dry skin. These compounds are designed to be hygroscopic and retain water to keep the stratum corneum hydrated, while at the same time enhancing the horny layer to prevent increases in transepidermal water loss (TEWL). Skin hydration levels, however, are known to influence barrier properties. The purpose of this work was to compare skin moisture levels induced by four commercially available moisturizing lotions with their capacity as transdermal penetration enhancers using the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as a model chemical. Further, the effect of moisturizing the skin after washing with sodium lauryl sulfate (SLS) on transdermal absorption was determined. Skin moisture levels were also measured noninvasively and were correlated to penetration enhancement. Hairless mouse skin was pretreated with commercially available moisturizing lotions either with or without SLS washing and in vitro permeability studies were performed with the herbicide 2,4-D. The data demonstrate that pretreatment with three of the four lotions tested increased the transdermal absorption of 2,4-D as evidenced by cumulative penetration or faster lag times (p < 0.05). Skin moisture levels correlated with the penetration enhancement capabilities of the lotion. Washing the skin with 5% SDS increased the transdermal absorption of 2,4-D (p < 0.05) and application of moisturizing lotions increased the absorption further. In summary moisturizing lotions may influence transdermal penetration of the skin, with the more effective moisturizers having a greater effect on 2,4-D absorption.

Golfer exposure to chlorpyrifos and carbaryl following application to turfgrass

Exposure of golfers to pesticides following their application to turfgrass is of concern to regulators, turfgrass professionals, and consumers. Multipathway exposures were evaluated for golfers on turfgrass treated with chlorpyrifos and carbaryl. Air concentrations and transferable foliar residues (TFRs) were measured to assess potential respiratory and dermal exposures, respectively. At the same time, exposure to individuals simulating the play of golf was determined by dosimetry and urinary biomonitoring. Individual golfer exposure was determined in 76 rounds of golf following eight applications of chlorpyrifos and two applications of carbaryl. Estimated exposures to golfers following full course and full rate applications of chlorpyrifos and carbaryl were 19-68 times below current U.S. EPA acute reference dose (Rfd) values, indicating safe exposures under U.S. EPA hazard quotient criteria. Dermal exposure was determined to be the dominant exposure pathway to golfers, accounting for approximately 60% of the chlorpyrifos absorbed dose and 100% of the carbaryl absorbed dose. This study also provides a set of transfer factors (TFs) that may be used to determine dermal exposure of golfers to pesticides using transferable residue data.

Transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid is enhanced by both ethanol consumption and sunscreen application

Xenobiotics absorption is a health concern and skin is a major exposure site for many of these chemicals. Both alcohol consumption and topical sunscreen application act as transdermal penetration enhancers for model xenobiotics. The effect of combining these two treatments on transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was therefore examined. Skin from rats ingesting low (1.5 g/kg) medium (4.3 g/kg) or high (6 g/kg) ethanol doses or saline control was treated with a commercially available sunscreen containing titanium dioxide and octyl methoxycinnimate and transdermal absorption of 2,4-D was monitored. Ethanol increased penetration by a factor of 1.9, 2.0 and 2.5 for animals treated with 1.5, 4.3 and 6 g/kg respectively, demonstrating an ethanol-induced dose response. Sunscreen application to skin from ethanol gavaged rats caused 2,4-D absorption above that induced by ethanol alone by an additional factor of 1.3, 2.1 and 2.9 for 1.5, 4.3 and 6 g/kg respectively. Comparing 2,4-D transdermal absorption after exposure to both ethanol and sunscreen with a theoretical value (sum of penetration after ethanol or sunscreen treatment) demonstrates that these two treatments enhance additively at the higher doses tested. Results of this study emphasize the importance of limiting excessive alcohol consumption in individuals with potential herbicide exposure rather than discouraging the use of sunscreens, since the consequences of UV-induced skin cancer are far more series than the risks that would be associated with observed increases in chemical exposure.

[Estrogenic activity of ultraviolet absorbers and the related compounds]

The estrogenic activities of ultraviolet absorbers and their related compounds were investigated using MCF-7 cell proliferation assay. Nine of 33 chemicals (benzophenone, 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 4-hydroxybenzophenone, 3-(4-methylbenzylidene) camphor, ethyl 2-cyano-3,3-diphenylacrylate (etocrylene) and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate (octocrylene)) were positive compared with the vehicle control. Benzhydrol, ethyl cinnamate and 2,2'-dihydroxy-4-methoxybenzophenone were weakly active. When each xenoestrogen was added to the cells along with ICI 182780, an estrogen receptor (ER) antagonist, the cell growth was reduced according to its doses. Therefore, the cell proliferation was suggested to generate through ER. Most of these chemicals were also positive using CHOOSER assay, a new method of testing estrogenic activity of xenoestrogen. Each xenoestrogen was also confirmed to bind to ERalpha and ERbeta using a human ER competitive binding assay against 17beta-estradiol. The concentration order of the strength of its inhibitory effect using both ERalpha and ERbeta was similar to that of MCF-7 cell proliferation assay, except for benzyl 4-hydroxybenzoate (B4HB). B4HB showed a stronger activity on CHOOSER assay and the competitive binding assay using both ERalpha and ERbeta, although there was no activity observed on MCF-7 cell proliferation assay. Our findings were to detect the estrogenic activity of etocrylene and octocrylene in vitro, in addition to confirming the activities of some ultraviolet absorbers as previously reported.

In vitro evaluation of concurrent use of commercially available insect repellent and sunscreen preparations

BACKGROUND

Insect repellents and sunscreens are over-the-counter products extensively used by the general public. Concurrent application of these products has become widespread in many regions across North America, because of concerns about West Nile virus and skin cancers.

OBJECTIVES

We investigated whether formulation type, application amount, and sequence would affect the percutaneous absorption profiles of the active repellent and sunscreen ingredients.

METHODS

In vitro percutaneous permeation of the repellent N,N-diethyl-m-toluamide (DEET) and the sunscreen oxybenzone from concurrent application of five commercially available products (A, repellent spray; B, repellent lotion; C, sunscreen lotion; D and E, combined repellent/sunscreen lotions) was measured and compared using Franz-style diffusion cells with piglet skin at 37 degrees C.

RESULTS

Penetration of DEET in A and B increased by 1640% and 282%, respectively, when C was applied concurrently. Penetration of DEET in D and E was 53% and 79% higher than that in B. Permeation of DEET from A + C (2:1) and A + C (1: 2) increased by 530% and 278%, respectively. Permeation of oxybenzone was 189% and 280% higher in A + C and B + C than in C. Permeation of oxybenzone in D and E was also 221% and 296% higher than that in C. Permeation of oxybenzone was 196% greater when A was applied on top of C than when C was applied on top of A, while oxybenzone in A + C (1:2) permeated 171% more than that in A + C (2:1).

CONCLUSIONS

Concurrent application of commercially available repellent and sunscreen products resulted in significant synergistic percutaneous permeation of the repellent DEET and the sunscreen oxybenzone in vitro. The percutaneous penetration profiles were dependent upon the type of formulation, application sequence and application proportion.

Active ingredients in sunscreens act as topical penetration enhancers for the herbicide 2,4-dichlorophenoxyacetic acid

Agricultural workers are encouraged to use sunscreen to decrease the risk of UV-related skin cancer. Our previous studies have shown certain commercial sunscreens to be penetration enhancers. The focus of this project is to determine whether active ingredients in sunscreen formulations (i.e., the UV absorbing components and insect repellants for the sunscreen/bug repellant combinations) also act as dermal penetration enhancers for herbicides in vitro. The total percentages of 2,4-dichlorophenoxyacetic acid (2,4-D) penetrating through hairless mouse skin in 24 h ranged from 54.9 +/- 4.7 for the no sunscreen control to 86.9 +/- 2.5 for padimate-o. Of the active ingredients tested (7.5% octyl methoxycinnamate, 7% octocrylene, 0.6% oxybenzone, 5% homosalate, 5% octyl salicylate, 8% padimate-o, 10% sulisobenzone, and 9.5% and 19% N,N-diethyl-m-toluamide [DEET]), all but octocrylene led to a significant increase in total 2,4-D penetration as compared to the control (P < 0.05), and only octocrylene and oxybenzone did not significantly decrease the corresponding lag time. Octyl salicylate (P < 0.01) and octyl methoxycinnimate (P < 0.05) significantly increased the 3H2O penetration across mouse skin, indicating physical damage to the stratum corneum. Additional studies demonstrated that the penetration enhancement seen across hairless mouse skin also occurred with human skin. Thus, the active ingredients of sunscreen formulations enhance dermal penetration of the moderately lipophilic herbicide 2,4-D.