Dermal exposure assessment in occupational medicine

An improved method for determining dermal exposure to polycyclic aromatic hydrocarbons

Many workers are occupationally exposed to polycyclic aromatic hydrocarbons (PAHs), which may cause various health problems, and some PAHs are known or suspected carcinogens. PAH exposure is primarily monitored by air sampling, but contamination may also occur through dermal exposure. PAHs adsorbed to the skin can be sampled by tape-stripping, but subsequent extraction of sampling tapes in organic solvent also releases diverse co-eluting substances that are difficult to remove before analysis of the PAHs by gas chromatography/mass spectrometry (GC/MS). The objective of this study was to optimise a procedure for analytical clean-up after extraction of 32 PAHs from tape-strips, by dialysis in organic solvent using semipermeable membranes. With triplicate subsamples, the developed method yields acceptable precision and repeatability for both the 32 PAHs, across the concentration range 10-160 ng per sample, and for a certified reference material (urban dust). The optimized clean-up procedure and GC/MS methodology was used to assess PAHs on skin from the lower part of the ventral side of the wrist and just below the collar bone of three firefighters and seven controls (office workers). Several gaseous and particle-bound PAHs were detected in all samples, including controls. Thus, the optimized procedure using semipermeable membranes for clean-up of tape-strip extracts can be used to assess the dermal exposure of both occupational and general populations to multiple PAHs. The results also show that both gaseous and particle-bound PAHs, including alkylated species, may be present on skin.

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.

Efficacy of predictive modeling as a scientific criterion in dermal hazard identification for assignment of skin notations

Skin notations (SNs) represent a hazard characterization tool for alerting workers of health hazards associated with dermal contact with chemicals. This study evaluated the efficacy of a predictive model utilized by the National Institute for Occupational Safety and Health to identify dermal hazards based on potential of systemic absorption compared to hazard assignments based on dermal lethal dose 50% or logarithm of octanol-water partition coefficient. A total of 480 chemicals assigned an SN from at least one of seven institutes were selected and partitioned into seven hazard categories by frequency of SN assignment to provide a basis of evaluation for the predictivity of the examined criteria. We find that all three properties serve as a qualitative indicator in support of a dichotomous decision on dermal hazard; the predictive modeling was identified from a multiple regression analysis as the most significant indicator. The model generated estimates that corresponded to anticipated hazard potentials, suggesting a role of the model to further serve as a hazard-ranking tool. The hazard-ranking capability of the model was consistent with the scheme of acute toxicity classification in the Globally Harmonized System of Classification and Labeling of Chemicals.

The evolution of skin notations for occupational risk assessment: a new NIOSH strategy

This article presents an overview of a strategy for assignment of hazard-specific skin notations (SK), developed by the National Institute for Occupational Safety and Health (NIOSH). This health hazard characterization strategy relies on multiple SKs capable of delineating systemic (SYS), direct (DIR), and immune-mediated (SEN) adverse effects caused by dermal exposures to chemicals. One advantage of the NIOSH strategy is the ability to combine SKs when it is determined that a chemical may cause multiple adverse effects following dermal contact (e.g., SK: SYS-DIR-SEN). Assignment of the SKs is based on a weight-of-evidence (WOE) approach, which refers to the critical examination of all available data from diverse lines of evidence and the derivation of a scientific interpretation based on the collective body of data including its relevance, quality, and reported results. Numeric cutoff values, based on indices of toxic potency, serve as guidelines to aid in consistently determining a chemical's relative toxicity and hazard potential. The NIOSH strategy documents the scientific rationale for determination of the hazard potential of a chemical and the subsequent assignment of SKs. A case study of acrylamide is presented as an application of the NIOSH strategy.

A simple dermal absorption model: derivation and application

This paper deals with the derivation of a QSAR for the estimation of: the skin permeation coefficient from aqueous solutions in cm h(-1), the stratum corneum/water partition coefficient. These QSARs enable the estimation of: the aqueous permeation coefficient in cm h(-1), the maximum dermal absorption in mg cm(-2) h(-1) from a saturated aqueous solution at steady state, the lag time in hours (h), the diffusivity of a substance in the stratum corneum in cm2 h(-1). By using the independent variables: the log(octanol/water partition coefficient), the molecular weight,the water solubility. The estimated maximum dermal absorption and the lag time were compared with some recent measured data of substances, which were not used for developing the QSARs. The estimates were generally in the same order of magnitude as the measured absorption and lag time. These QSARs are recommended for risk assessment of chemicals in the scope of the European REACH legislation.

Background, approaches and recent trends for setting health-based occupational exposure limits: a minireview

The setting of occupational exposure limits (OELs) are founded in occupational medicine and the predictive toxicological testing, resulting in exposure-response relationships. For compounds where a No-Observed-Adverse-Effect-Level (NOAEL) can be established, health-based OELs are set by dividing the NOAEL of the critical effect by an overall uncertainty factor. Possibly, the approach may also be used for carcinogens if the mechanism is epigenetic or the genetic effect is secondary to effect from reactions with proteins such as topoisomerase inhibitors, and mitotic and meiotic spindle poisons. Additionally, the NOAEL approach may also be used for compounds with weak genotoxic effect, playing no or only a minor role in the development of tumours. No health-based OEL can be set for direct-acting genotoxic compounds where the life-time risks may be estimated from the low-dose linear non-threshold extrapolation, allowing a politically based exposure level to be set. OELs are set by several agencies in the US and Europe, but also in-house in major chemical and pharmaceutical companies. The benchmark dose approach may in the future be used where it has advantage over the NOAEL approach. Also, more attention should be devoted to sensitive groups, toxicological mechanisms and interactions as most workplace exposures are mixtures.

How to improve skin notation. Position paper from a workshop

The ICOH Scientific Committee on Occupational and Environmental Dermatoses organized an International Workshop on "Dermal risk assessment at workplace" with the aim of focussing on the different ways of approaching the concept of skin notation (S) for chemicals. The Workshop participants presented their ideas on several aspects of S such as the problems related to the absorption through the compromised skin, the different approaches to S and models that can be used as alternatives to S. Participants agreed to produce a position paper with the goal of exploring the actions needed to improve the S system towards international harmonization. They consider that further discussions are needed to obtain an international consensus, but at the same time they believe that by improving and harmonizing systems for setting S we can make an important contribution to improving health of people with potential dermal exposure to chemicals at work.

Environmental and biological monitoring of exposure to organophosphorus pesticides: application to occupationally and non-occupationally exposed adult populations

The purpose of the study was to assess non-dietary exposure of workers and the general population in the Paris area to some organophosphorus (OP) pesticides. In total, 21 workers from different occupational places (two greenhouses, three florist shops and three veterinary departments) and 20 subjects assumed to be non-occupationally exposed were recruited. Indoor air, hand wipes, and three first morning urine samples were collected. Seven OPs were measured by GC/ECD and GC/TSD, and six urinary dialkylphosphate metabolites by GC/PFPD. All indoor air samples from the workplaces and only one-third of the samples from the residences contained at least one of the seven OPs. However, almost all participants were dermally exposed to OPs. Total OP indoor air and cutaneous levels were significantly higher for workers than for the general population (air median = 185 pmol/m3 versus nondetectable, P < 0.0001; hands median = 1250 pmol/hands versus 475 pmol/hands, P = 0.03). From the air, gardeners and florists were mainly exposed to methyl-OPs and veterinary staff to ethyl-OPs (mainly diazinon). From their hands, all subjects were exposed to methyl-OPs, with gardeners and florists exposed to somewhat but not significantly higher levels. Ethyl-OPs were more found frequently and at higher levels on the hands of veterinary workers. Total OP levels in indoor air and from hand wipes were significantly correlated (Spearman R = 0.34, P = 0.03). DAP detection frequencies and levels were not different between workers and the general population (workers median=168 nmol/g creat and general population median = 241 nmol/g creat, P = 0.31), and did not correlate with air or hand levels. Subjects not occupationally exposed showed significant residential exposure to OPs, more frequently from their hands than from the air. Different occupations were associated with different exposure profiles and levels. The lack of differences in DAP levels between the different groups of exposure suggests that dietary exposure to OP residues and exposure to other OPs are involved.

A Dermatotoxicokinetic Model of Human Exposures to Jet Fuel

Workers, both in the military and the commercial airline industry, are exposed to jet fuel by inhalation and dermal contact. We present a dermatotoxicokinetic (DTK) model that quantifies the absorption, distribution, and elimination of aromatic and aliphatic components of jet fuel following dermal exposures in humans. Kinetic data were obtained from 10 healthy volunteers following a single dose of JP-8 to the forearm over a surface area of 20 cm2. Blood samples were taken before exposure (t = 0 h), after exposure (t = 0.5 h), and every 0.5 h for up to 3.5 h postexposure. The DTK model that best fit the data included five compartments: (1) surface, (2) stratum corneum (SC), (3) viable epidermis, (4) blood, and (5) storage. The DTK model was used to predict blood concentrations of the components of JP-8 based on dermal-exposure measurements made in occupational-exposure settings in order to better understand the toxicokinetic behavior of these compounds. Monte Carlo simulations of dermal exposure and cumulative internal dose demonstrated no overlap among the low-, medium-, and high-exposure groups. The DTK model provides a quantitative understanding of the relationship between the mass of JP-8 components in the SC and the concentrations of each component in the systemic circulation. The model may be used for the development of a toxicokinetic modeling strategy for multiroute exposure to jet fuel.

Contaminación externa de viales de metotrexato detectada en un hospital argentino

OBJECTIVE

To quantify external contamination of methotrexate vials and alert about occupational health hazards.

METHOD

All 50 mg and 500 mg methotrexate vials were opened and cleaned with an alcohol wet white wipe in February 2005. The vials were divided in two groups according to visual external contamination or not. The air tightness of the vials was stated.

RESULTS

9.33% methotrexate vials were contaminated under visual inspection. Two of five manufacturers presented contaminated vials. The proportion of contaminated vials in the two former manufacturers was 18.8 and 21.43%.

CONCLUSIONS

External contamination would be due to manufacture processes. Cutaneous absorption is very important because of the contamination founded. It s strongly recommended that all personal involved in cytotoxic handling take protection measures.

Total body burden arising from a week's repeated dermal exposure to N,N-dimethylformamide

BACKGROUND

Hazardous chemicals and their metabolites may accumulate in the body following repeated airborne exposures and skin contact.

AIMS

To estimate the contribution of skin absorption to total body burden of N,N-dimethylformamide (DMF) across a working week in two groups with similar levels of respiratory exposure but dissimilar skin contact.

METHODS

Twenty five workers in a synthetic leather (SL) factory, 20 in a copper laminate circuit board (CLCB) factory, and 20 age and sex matched non-DMF exposed subjects, were recruited. Environmental monitoring of DMF exposure via respiratory and dermal routes, as well as biological monitoring of pre-shift urinary N-methylformamide (U-NMF), were performed for five consecutive working days.

RESULTS

Environmental and biological monitoring showed no detectable exposure in controls. The average airborne DMF concentration (geometric mean (GM) 3.98 ppm, geometric standard deviation (GSD) 1.91 ppm), was insignificantly lower for SL workers than for CLCB workers (GM 4.49, GSD 1.84 ppm). Dermal DMF exposure and U-NMF values, however, were significantly higher for SL workers. A significant pattern of linear accumulation was found across a five day work cycle for SL workers but not for CLCB workers.

CONCLUSIONS

Dermal exposure to DMF over five consecutive days of occupational exposure can result in the accumulation of a significant DMF body burden. The long term exposure response under both repeated and intermittent conditions of substantial skin exposure is worthy of note.