The Duke Toxicology Program both evaluates human health risks associated with consumer product use and conducts studies on consumer use to compliment or validate our risk assessment approach. Materials that are of regulatory concern are also evaluated by this program including lead and asbestos. Studies that have been conducted by this program include assessment of bioaccessibility of various metals found in art materials with skin or mouth contact; hand-to- mouth transfer of art materials; and solvent exposure during use of markers with solvent-based inks. In addition, the Duke Toxicology Program conducts research for refining and validating its risk assessment approaches for human health endpoint based on the latest science available. Below are some highlights of Duke’s research efforts.
Skin Sensitizers and Irritants
Quantitative Evaluation of Skin Sensitizers and Irritants
A Protocol for Assessing Dermal Exposures While Using Pressurized Aerosol Sprays, Airbrushing and Drawing with Pastels was developed that uses a quantitative risk assessment approach for evaluating skin sensitizers and irritants for which human patch test results are available. Two examples of such an approach are the risk assessment for isothiazolinones and formaldehyde-releasing preservatives.
Quantitative Assessment of Skin Allergens
Acceptable levels of allergens have been determined by the percentage of the allergen that can be used without resulting in an allergic reaction. Human insult patch testing has shown that the risk of an allergic reaction is related to the amount of allergen that comes into contact with the skin surface. This approach to the quantitative assessment of allergens is detailed in a 2013 paper entitled “Quantitative Risk Assessment of Skin Sensitizers and Irritants”
Benzoisothiazolinone Action Level
The action level for benzisothiazolinone, a preservative, has been decreased to 470 ppm in art materials based on human testing showing irritation and sensitization potential at higher levels.
Natural Rubber Latex
ACMI requires labeling for natural rubber latex sensitization hazards in all liquid products containing natural rubber latex and in artists’ rubber erasers containing natural rubber latex. Recent studies have shown extractable rubber latex antigen in this type of eraser. Studies have been conducted looking for extractable rubber latex antigen in erasers containing <10% natural rubber latex.
Lead in Consumer Products
State and federal regulations require that lead levels in children’s products meet certain standards. Current test methods for determining total lead may determine values that erroneously low because of plastic matrix effects. The 2008 paper “Comparison of testing of plastics for lead by x-ray fluorescence and traditional nitric acid digestion/ GFAA after muffle furnace combustion” identifies methods that can accurately detect total lead levels in plastics.
Lead is found in all ball point pen tips above the total lead levels specified in a new consumer safety law (CPSIA). The 2009 study “Bioaccessibility of Lead in Metal Pen Tips” addresses whether or not exposure and absorption of lead in such tips can occur.
A number of studies of lead-containing materials have been conducted to support the use of bioaccessibility testing as means for determining chronic risk from metals contained in ingested materials. The following papers summarize these studies. The 2017 research report “Comparison of the Solubility of Lead in Various Materials and Its Bioavailability” compares the results of feeding studies of lead-containing ores with bioaccessibility testing of these ores. A second paper, “Factors affecting the solubility of metals in art materials,” addresses a mass ion effect seen when there is an excess extractant volume is used for testing.
Ceramic Glaze Exposures
Contemporary ceramic studios offer a venue for ceramic decorating to both children and adults. Although decorating is done with lead-free glazes, completed pieces are usually dipped in a leaded-glaze and fired. The study “Lead Contamination in Contemporary Ceramics Studios: Potential for Community and Worker Exposure” has shown the potential for lead exposure to both workers and patrons that can be controlled with change in practices.
Connecticut found that leaded glazes were being used in school systems even below the high school level. The paper “Classroom Contamination from Lead Bearing Ceramic Art Glaze” gives details of lead exposures in 13 schools and 18 art rooms where lead contamination occurred.
Lead exposures in ceramic studios can be monitored by wipe testing. EPA has set an acceptable level of 40 micrograms/m2 for children. But, as seen in the paper “Identifying Lead Dust Contamination Limits Appropriate for Adults and Older Children,” an acceptable exposure level for adults may be much higher.
A 2006 study determined the magnitude of hand contamination and hand-to-mouth transfer with intensive ceramic decorating activities by finger, sponge or brush. Read “Determination of the Magnitude of Ceramic Glaze to Skin and Skin to Mouth Transfer.”
A number of ceramic glazes use metal-based stains as colorants. Their potential for skin absorption relates to their solubility.
Boric Acid Risk Assessment
Soluble boron, in the form of boric acid, can cause acute brain damage and/or seizures with ingestion of large amounts over short periods of time. With chronic exposures there is a risk of fetal toxicity and testicular effects with decreased fertility. A risk assessment evaluates new knowledge on the toxicity of boron with a focus on chronic developmental and reproductive toxicity.
Evaluation of Aerosol Sprays
Canada’s Consumer Chemical and Containers Regulations, 2001 specifies that products containing >10% low viscosity compounds (certain hydrocarbons, alcohols and ketones that present aspiration risks) must have child-resistant packaging except a spray container that cannot be opened and that disperses the product as a mist. Duke Toxicity developed a test methodology for determining aspiration hazards of aerosol sprays describes the development of a test method to determine whether or not an aerosol spray is a mist and reports on tests of a wide variety of aerosol products.
Evaluation of Respirable Particle Exposures
The Duke Toxicology Program has completed a number of studies to measure aerosol production during various art and craft activities. The report “Aerosol Production During the Use of Art and Craft Materials” details these studies and uses them to model aerosol exposures associated with these activities.
Pastel Dust Exposures
The evaluation of dusts produced from the use and cleanup of art works made with pastels and chalk are discussed in a paper entitled “ Risk Assessment for Exposure to Respirable Dusts Generated from the Use of Chalks and Pastels”
Testing for Spontaneous Combustion Risk
Rags soaked with linseed oil present a risk of spontaneous combustion. In the past two decades, a number of oils have been developed to substitute for or amend linseed oil, including safflower oil and walnut oil. ASTM has developed method D6801 to test for spontaneous combustion risk. This method was initially used to evaluate linseed oil-based products but now has been extended to the evaluation of a wide variety of oils and products, including those used in the art material field, wood refinishing and foods.
Titanium dioxide is a white pigment widely used in art materials. An assessment by Duke Toxicology of the potential of exposures to titanium dioxide to be associated with a risk of lung tumors in man has been submitted to the California's Office of Environmental Health Hazard Assessment.
Duke Toxicology was involved in a 2003 study “Determination of the Magnitude of Clay to Skin to Mouth Transfer of Phthalates Associated with the Use of Polymer Clays” investigates hand contamination when using polymer clay, both in the laboratory and by professional polymer clay artists, and addresses the potential for incidental ingestion of phthalate esters associated with hand contamination.
Risk Assessment for Phthalates in Polymer Clays
The National Toxicology Program (NTP) has completed a re-assessment of the hazards associated with exposure to some phthalate esters. Some of these phthalate esters are used as plasticizers in polymer clays, which are modeling clays that are heat set at a low temperature. Duke Toxicology performed a risk assessment of hazards associated with the use and curing of these clays includes NTP findings as well as test information for the potential for phthalates to be released during curing.
ATSDR has proposed a minimum risk level (MRL) for soluble cobalt based upon a therapeutic effect, increases in hemoglobin. Duke Toxicology recommends that toxicity-related endpoints, cardiomyopathy and thyroid dysfunction, be used to determine the MRL.
A risk assessment based on this approach has been published in the following paper:
- Brock T, Stopford W. Bioaccessibility of metals in human health risk assessment: Evaluating risk from exposure to cobalt compounds. J Environ Management. 2003; 3(5):71N-76N
The bioaccessibility (solubility) of cobalt compounds using various media, including synthetic intestinal juice, is studied in the following paper:
- Stopford W, Turner J, Cappellini D, Brock T. Bioaccessibility testing of cobalt compounds. J Environ Management. 2003; 3(5):675-680.
Duke toxicologists have completed three studies that examine solvent exposures to users of solvent-based markers. The last study, which will be finalized in 2021, covers the academic year 2019-2020 and the impact of COVID-19 and school closures on marker use.
- “Solvent Exposure to Graphic Artists” examines xylene exposure from professional use of xylene-based markers by graphic artists. Findings include that the maximum exposure to xylene averaged 0.5 ppm, even when use was for as much as 210 minutes a day or an average of 102 minutes a day.
- “Solvent Exposure During Use of Solvent-Based Whiteboard Markers” examines solvent exposure from simulated classroom activities involving solvent-based whiteboard markers. Exposures projected to 25 users working simultaneously in a poorly ventilated classroom showed low exposures.
Asbestiform Fibers in Crayons
Concern has been raised because of the finding of asbestiform fibers that are chemically transitional between asbestos and in talcs used to make crayons. Read more about this issue on the ACMI website.