Octamethylcyclotetrasiloxane exhibits estrogenic activity in mice via ERα

Indoor Air Pollution by Methylsiloxane in Household and Automobile Settings

This study examines characteristics of atmospheric methylsiloxane pollution in indoor settings where interior renovation/redecoration is being undertaken, in addition to ordinary family homes and inside family cars. Concentrations of atmospheric methylsiloxane in these locations were approximately one order of magnitude higher than that in outdoor areas. The average indoor concentration of methylsiloxane where renovation was being undertaken was 9.4 μg/m3, which is slightly higher than that in an ordinary family home (7.88 μg/m3), while samples from family cars showed lower concentration (3.10 μg/m3). The indoor atmospheric concentration during renovation/redecoration work was significantly positively correlated with the duration of the work. The structure of atmospheric methylsiloxane pollution is basically the same in these three venues. The concentration of annulus siloxane was much higher than that of linear compounds (85% of the total methylsiloxane concentrations). Household dust in average family homes showed total methylsiloxane concentration of 9.5 μg/m3 (average); the structure mainly consisted of linear siloxane (approximately 98% of total concentration), thereby differing from that of atmospheric methylsiloxane pollution. The comparatively high concentration of methylsiloxane in these three venues indicates that interior renovation and decoration work, and even travelling in cars, can involve exposure to more serious siloxane contamination during everyday activities.

A survey of cyclic and linear siloxanes in indoor dust and their implications for human exposures in twelve countries

Siloxanes are used widely in a variety of consumer products, including cosmetics, personal care products, medical and electrical devices, cookware, and building materials. Nevertheless, little is known on the occurrence of siloxanes in indoor dust. In this survey, five cyclic (D3-D7) and 11 linear (L4-L14) siloxanes were determined in 310 indoor dust samples collected from 12 countries. Dust samples collected from Greece contained the highest concentrations of total cyclic siloxanes (TCSi), ranging from 118 to 25,100ng/g (median: 1380), and total linear siloxanes (TLSi), ranging from 129 to 4990ng/g (median: 772). The median total siloxane (TSi) concentrations in dust samples from 12 countries were in the following decreasing order: Greece (2970ng/g), Kuwait (2400), South Korea (1810), Japan (1500), the USA (1220), China (1070), Romania (538), Colombia (230), Vietnam (206), Saudi Arabia (132), India (116), and Pakistan (68.3). TLSi concentrations as high as 42,800ng/g (Kuwait) and TCSi concentrations as high as 25,000ng/g (Greece) were found in indoor dust samples. Among the 16 siloxanes determined, decamethylcyclopentasiloxane (D5) was found at the highest concentration in dust samples from all countries, except for Japan and South Korea, with a predominance of L11; Kuwait, with L10; and Pakistan and Romania, with L12. The composition profiles of 16 siloxanes in dust samples varied by country. TCSi accounted for a major proportion of TSi concentrations in dust collected from Colombia (90%), India (80%) and Saudi Arabia (70%), whereas TLSi predominated in samples collected from Japan (89%), Kuwait (85%), and South Korea (78%). Based on the measured median TSi concentrations in indoor dust, we estimated human exposure doses through indoor dust ingestion for various age groups. The exposure doses ranged from 0.27 to 11.9ng/kg-bw/d for toddlers and 0.06 to 2.48ng/kg-bw/d for adults.

Occurrence of cyclic and linear siloxanes in indoor air from Albany, New York, USA, and its implications for inhalation exposure

Cyclic and linear siloxanes are used in a wide variety of household and consumer products. Nevertheless, very few studies have reported the occurrence of these compounds in indoor air or inhalation exposure to these compounds. In this study, five cyclic (D3-D7) and nine linear siloxanes (L3-L11) were determined in 60 indoor air samples collected in Albany, New York, USA. The mean concentrations of individual siloxanes in particulate and vapor phases ranged from <12 μg g(-1) (for octamethyltrisiloxane [L3], decamethyltetrasiloxane [L4]) to 2420 μg g(-1) (for decamethylcyclopentasiloxane [D5]) and from 1.05 ng m(-3) to 543 ng m(-3), respectively. The mean concentrations of individual siloxanes in combined particulate and vapor phases of bulk indoor air ranged from 1.41 ng m(-3) (for L4) to 721 ng m(-3) (for D5). Cyclic siloxanes hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), D5, dodecamethylcyclohexasiloxane (D6), and octadecamethylcycloheptasiloxane (D7) were found in all indoor air samples. The mean concentrations of total siloxanes (i.e., sum of cyclic and linear siloxanes) ranged from 249 ng m(-3) in laboratories to 6210 ng m(-3) in salons, with an overall mean concentration of 1470 ng m(-3) in bulk indoor air samples. The calculated mean daily inhalation exposure doses of total siloxanes (sum of 14 siloxanes) for infants, toddlers, children, teenagers, and adults were 3.18, 1.59, 0.76, 0.34, and 0.27 μg/kg-bw/day, respectively.

Methyl siloxanes in environmental matrices and human plasma/fat from both general industries and residential areas in China

We investigated human exposure to methyl siloxanes in three general industries (building, automobile, and textile industries) and residential areas in China. Usage volumes of methyl siloxanes per capita in these industries were 2-5 orders of magnitudes higher than those in residential areas. Methyl siloxane concentrations in indoor air and dust samples from industrial facilities were 1-3 orders of magnitudes higher than those in residential houses. Both cyclic (D4-D6) and linear (L5-L16) siloxanes were detected in plasma of industrial workers (1.00-252 ng/mL, detection frequencies=3.7-71%, n=528), while only cyclic compounds (D4-D6) were detected in plasma of general population (n=519) with much lower concentrations (1.10-7.50 ng/mL) and detection frequencies (1.7-3.7%). During the occupational exposure, anti-dust mask can reduce 30% of intake of cyclic siloxanes and 74% of intake of linear siloxanes, respectively. In addition, PM-10 could elevate intake of linear siloxanes. Calculated fat-plasma partition ratios of methyl siloxanes (D4-D6, L6-L11) in the present study were 5.3-241 mL/g. Linear rather than cyclic siloxanes had an apparent accumulation in abdominal fat. Population's half-lives of L8-L10 in abdominal fat of general population were approximately 1.49-1.80 years.

Effect of silicone on the collagen fibrillogenesis and stability

Collagen, the most abundant protein in mammals, is able to form fibrils, which have central role in tissue repair, fibrosis, and tumor invasion. As a component of skin, tendons, and cartilages, this protein contacts with any implanted materials. An inherent problem associated with implanted prostheses is their propensity to be coated with host proteins shortly after implantation. Also, silicone implants undergoing relatively long periods of contact with blood can lead to formation of thrombi and emboli. In this paper, we demonstrate the existence of interactions between siloxanes and collagen. Low-molecular-weight cyclic siloxane (hexamethylcyclotrisiloxane—D3) and polydimethylsiloxanes (PDMS) forming linear chains, ranging in viscosity from 20 to 12,000 cSt, were analyzed. We show that D3 as well as short-chain PDMS interact with collagen, resulting in a decrease in fibrillogenesis. However, loss of collagen native structure does not occur because of these interactions. Rather, collagen seems to be sequestered in its native form in an interlayer formed by collagen–siloxane complexes. On the other hand, silicone molecules with longer chains (i.e., PDMS with viscosity of 1000 and 12,000 cSt, the highest viscosity analyzed here) demonstrate little interaction with this protein and do not seem to affect collagen activity. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1275–1281, 2015

Cyclotetrasiloxane frameworks for the chemoenzymatic synthesis of oligoesters

The lipase-mediated synthesis of branched and polycyclic polyester systems based on a cyclotetrasiloxane core.

A nationwide survey and emission estimates of cyclic and linear siloxanes through sludge from wastewater treatment plants in Korea

Siloxanes are widely used in various industrial applications as well as in personal care products. Despite their widespread use and potential toxic effects, few studies have reported on the occurrence of siloxanes in the environment. In this study, we determined the concentrations of 5 cyclic and 15 linear siloxanes in sludge collected from 40 representative wastewater treatment plants (WWTPs) in Korea. Total concentrations of 20 siloxanes (Σsiloxane) in sludge ranged from 0.05 to 142 (mean: 45.7) μg/g dry weight, similar to the concentrations reported in European countries but higher than those reported in China. The concentrations of siloxanes in sludge from domestic WWTPs were significantly (p<0.01) higher than those from industrial WWTPs, indicating higher consumption of siloxanes in various personal care products (e.g. shampoos and conditioners). The major siloxane compounds found in sludge were decamethylcyclopentasilane (D5), docosamethyldecasiloxane (L10) and dodecamethylcyclohexasilane (D6), which collectively accounted for, on average, 62% of the Σsiloxane concentrations. Non-parametric multidimensional scaling ordination of the profiles of siloxanes indicated the existence of different usage patterns of siloxanes between industrial and household activities. Multiple linear regression analysis of siloxane concentrations and WWTP characteristics suggested that D5, D6 and linear siloxane concentrations in sludge were positively correlated with population served by a WWTP. Environmental emission fluxes of cyclic and linear siloxanes through sludge disposal in Korea were 14,800 and 18,500 kg/year, respectively. This is the first report describing occurrence and environmental emission of siloxanes through sludge in Korea.

Temporal variations of cyclic and linear volatile methylsiloxanes in the atmosphere using passive samplers and high-volume air samplers

Cyclic and linear volatile methylsiloxanes (cVMSs and lVMSs, respectively) were measured in ambient air over a period of over one year in Toronto, Canada. Air samples were collected using passive air samplers (PAS) consisting of sorbent-impregnated polyurethane foam (SIP) disks in parallel with high volume active air samplers (HV-AAS). The average difference between the SIP-PAS derived concentrations in air for the individual VMSs and those measured using HV-AAS was within a factor of 2. The air concentrations (HV-AAS) ranged 22-351 ng m(-3) and 1.3-15 ng m(-3) for ΣcVMSs (D3, D4, D5, D6) and ΣlVMSs (L3, L4, L5), respectively, with decamethylcyclopentasiloxane (D5) as the dominant compound (∼75% of the ΣVMSs). Air masses arriving from north to northwest (i.e., less populated areas) were significantly less contaminated with VMSs compared to air arriving from the south that are impacted by major urban and industrial areas in Canada and the U.S. (p < 0.05). In addition, air concentrations of ΣcVMSs were lower during major snowfall events (on average, 73 ng m(-3)) in comparison to the other sampling periods (121 ng m(-3)). Ambient temperature had a small influence on the seasonal trend of VMS concentrations in air, except for dodecamethylcyclohexasiloxane (D6), which was positively correlated with the ambient temperature (p < 0.001).

Distribution, source, fate and bioaccumulation of methyl siloxanes in marine environment

Studies have shown that some cyclic methyl siloxanes were identified as characterized of persistent, bioaccumulated, toxic, and potential to ecological harm. In this study, we determined methyl siloxanes in seawater, sediment and bottom fish samples collected from marine environment in Northeast China. The mean concentrations of total methyl siloxanes were 46.1 ± 27.2 ng/L, 12.4 ± 5.39 ng/g dry weight (dw) and 5.10 ± 1.34 wet weight (ww) in seawater, sediment and fish, respectively. Very strong and significant correlations (r = 0.94, p < 0.0001) were found in compositions of methyl siloxanes between seawater and sewage, indicating that sewage was the main source of methyl siloxanes in the marine area studied. It was found that the mean value of biota-sediment accumulation factor (BSAF) was.0.716 ± 0.456 for D4, 0.103 ± 0.0771 for D5, 1.06 ± 0.528 for D6 and 0.877 ± 0.530 for D7.

Review of recent advances in research on the toxicity, detection, occurrence and fate of cyclic volatile methyl siloxanes in the environment

The fate and behavior of cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in the environment were reviewed. We evaluated their usage data and patterns, physico-chemical properties, toxicology, partitioning and degradation, methods of detection, and concentrations. The use of cVMS as an intermediate in the formation of silicone polymers, personal care and household products has resulted in their widespread environmental exposure; they have been detected in biogas, air, water, soil, biosolid, sediment, and biota samples. Modeled and experimental results suggest that cVMS may be subject to long-range atmospheric transport, but have low potential to contaminate the Arctic. For D4 and D5, there was no evidence of trophic biomagnification in aquatic food webs, while some aquatic organisms demonstrated a high degree of bioconcentration and bioaccumulation. High concentrations of cVMS observed in indoor air and biosolids resulted from point sources. Concentrations of cVMS in water, sediment, and soil were all below their no-observed-effect-concentrations.

Occurrence of linear and cyclic volatile methyl siloxanes in indoor air samples (UK and Italy) and their isotopic characterization

The occurrence of linear- and cyclic-volatile methyl siloxanes (lVMSs and cVMSs, respectively) in various indoor environments, occupational and domestic, in Italy and in the United Kingdom was studied. The results show that the cVMSs are the most abundant, detected in average concentrations that in some cases were as high as 170μgm(-3). Our study highlights the differences that can be observed between various indoor environments (e.g. domestic like bathrooms, bedrooms, or occupational) and between two countries. In most cases, the concentrations found in the UK are higher than in the respective indoor environments in Italy. The assessment of exposure to these two countries for adults and children revealed significant differences both not only in the levels of exposure, but also in the patterns. In Italy, the biggest part of the exposure to VMSs takes place domestically, whereas in the UK, it is observed for occupational environments. Additionally, the compound specific isotopic analysis was employed as a source identification technique. The results are promising mainly for D5 that occurs in higher concentrations, but not for the less abundant lVMSs and cVMSs.

Mass loading and fate of linear and cyclic siloxanes in a wastewater treatment plant in Greece

The occurrence and fate of 5 cyclic (D3 to D7) and 12 linear (L3 to L14) siloxanes were investigated in raw and treated wastewater (both particulate and dissolved phases) as well as in sludge from a wastewater treatment plant (WWTP) in Athens, Greece. Cyclic and linear siloxanes (except for L3) were detected in all influent wastewater and sludge samples at mean concentrations of (sum of 17 siloxanes) 20 μg L(-1) and 75 mg kg(-1), respectively. The predominant compounds in wastewater were L11 (24% of the total siloxane concentration), L10 (16%), and D5 (13%), and in sludge were D5 (20%) and L10 (15%). The distribution of siloxanes between particulate and dissolved phases in influents differed significantly for linear and cyclic siloxanes. Linear siloxanes showed higher solid-liquid distribution coefficients (log K(d)) than did cyclic compounds. For 10 of the 16 compounds detected in influents, the removal efficiency was higher than 80%. Sorption to sludge and biodegradation and/or volatilization losses are important factors that affect the fate of siloxanes in WWTPs. The mean total mass of siloxanes that enter into the WWTP via influent was 15.1 kg per day(-1), and the mean total mass released into the environment via effluent was 2.67 kg per day(-1).

Methyl siloxanes in environmental matrices around a siloxane production facility, and their distribution and elimination in plasma of exposed population

In this study, we systematically investigated methyl siloxanes (D4-D6, L3-L16) exposure to workers from and residents living near a siloxanes manufacturing facility by measuring their concentrations in both environmental matrices (air, dust/soil, n = 62) and human plasma samples (n = 201). For the seventeen target compounds, the average concentrations in indoor matrixes from six workshops of the facility ranged from 0.6 μg/m(3) to 2.7 mg/m(3) in air samples and from 0.36 μg/g to 1.16 mg/g in dust samples, which were 3-5 orders of magnitudes higher than those levels at the reference zone. In plasma samples from the current workers in six workshops and residents living near the facility, the average concentrations of methyl siloxanes were 5.61-451 and 4.56-13.5 ng/g, respectively, which were 1-2 magnitudes higher than those in the reference group. Plasma methyl siloxanes concentrations of people from different workshops were positively correlated with their exposure levels, indicating that high occupational exposure in siloxane production process elevated human plasma concentrations. However, there was no significant correlation between human plasma concentrations with their duration of occupation. These methyl siloxanes were eliminated from human plasma with half-lives ranging from 2.34 to 9.64 days, which increased with the increasing number of Si-O bonds for most analogues.

Cosmetics as a potential source of environmental contamination in the UK

Chemicals of emerging concern (CECs) are frequently used in cosmetic formulations and can potentially reach the environment at concentrations that may cause harm. A methodology was developed to assess over 120 chemicals assembled from product ingredient listings to identify and validate potential CECs in cosmetics, based on Annex XIII of REACH legislation. Ten potential CECs were identified: polydimethylsiloxane, butylated hydroxylanisole (BHA), butylated hydroxytoluene, triclosan, nano titanium dioxide, nano zinc oxide, butylparaben, diethyl phthalate, octinoxate methoxycinnamate and benzophenone. These chemicals were quantified based on their consumption and concentrations in cosmetics and percentage market penetration. The initial predicted environmental concentrations (PEC initial) were estimated to determine their exposure to the environment. With the exception of BHA, the PEC initial highlighted levels of exposure to the environment that triggered the need for further investigation of the chemicals. These chemicals were linked to cosmetics to highlight products with the potential to cause environmental harm. Skin care products had the highest quantities of CECs, with titanium dioxide and zinc oxide nanomaterials being dominant potential contaminants. Further research is required to assess the exposure pathways and fate of these chemicals to determine environmental risks associated with their use and disposal.

Safety Assessment of Cyclomethicone, Cyclotetrasiloxane, Cyclopentasiloxane, Cyclohexasiloxane, and Cycloheptasiloxane

Cyclomethicone (mixture) and the specific chain length cyclic siloxanes (n = 4-7) reviewed in this safety assessment are cyclic dimethyl polysiloxane compounds. These ingredients have the skin/hair conditioning agent function in common. Minimal percutaneous absorption was associated with these ingredients and the available data do not suggest skin irritation or sensitization potential. Also, it is not likely that dermal exposure to these ingredients from cosmetics would cause significant systemic exposure. The Cosmetic Ingredient Review Expert Panel concluded that these ingredients are safe in the present practices of use and concentration.

Analysis of linear and cyclic methylsiloxanes in water by headspace-solid phase microextraction and gas chromatography-mass spectrometry

This paper proposes a new method for the analysis of linear and cyclic methylsiloxanes in water samples based on headspace-solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The extraction efficiency of four commercially available SPME-fibres was evaluated and it was found that a 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) coating was the most suitable for the extraction of siloxanes. The method provided good linearity (r>0.999) and precision (RSD % <17%), and low limits of quantification ranging from 0.01 to 0.74 ng L(-1) for linear siloxanes and between 18 and 34 ng L(-1) for cyclic siloxanes. The HS-SPME-GC-MS method was applied to the analysis of linear and cyclic siloxanes in river waters from Catalonia (NE, Spain) and the results showed concentrations of linear and cyclic siloxanes ranging from 0.09 to 3.94 ng L(-1) and 22.2 to 58.5 ng L(-1), respectively.

Global distribution of linear and cyclic volatile methyl siloxanes in air

The global distribution of linear and cyclic volatile methyl silxoanes (VMS) was investigated at 20 sites worldwide, including 5 locations in the Arctic, using sorbent-impregnated polyurethane foam (SIP) disk passive air samplers. Cyclic VMS are currently being considered for regulation because they are high production volume chemicals that are potentially persistent, bioaccumulative, and toxic. Linear and cyclic VMS (including L3, L4, L5, D3, D4, D5, and D6) were analyzed for in air at all urban, background, and Arctic sites. Concentrations of D3 and D4 are significantly correlated, as are D5 and D6, which suggests different sources for these two pairs of compounds. Elevated concentrations of D3 and D4 on the West coast of North America and at high elevation sites suggest these sites are influenced by trans-Pacific transport, while D5 and D6 have elevated concentrations in urban areas, which is most likely due to personal care product use. Measured concentrations of D5 were compared to modeled concentrations generated using both the Danish Eulerian Hemispheric Model (DEHM) and the Berkeley-Trent Global Contaminant Fate Model (BETR Global). The correlation coefficients (r) between the measured and modeled results were 0.73 and 0.58 for the DEHM and BETR models, respectively. Agreement between measurements and models indicate that the sources, transport pathways, and sinks of D5 in the global atmosphere are fairly well understood.

Occurrence of cyclic and linear siloxanes in indoor dust from China, and implications for human exposures

Siloxanes are used in a wide variety of personal-care and other consumer products. Although there is clearly a potential for contamination of indoor dust with siloxanes, reports of occurrence of siloxanes in indoor dust were not available, prior to the present study. Here, we have determined the concentrations and profiles of four cyclic siloxanes, octamethylcyclotetrasiloxane (D(4)), decamethylcyclopentasiloxane (D(5)), dodecamethylcyclohexasiloxane (D(6)), and tetradecamethylcycloheptasiloxane (D(7)), as well as 11 linear siloxanes, from L(4)-L(14), in 100 dust samples collected in China. Cyclic and linear siloxanes were found in all dust samples, with the linear siloxanes L(9)-L(14) being the predominant compounds. Concentrations of total siloxanes in dust ranged from 21.5 to 21,000 (mean: 1540 +/- 2850) ng g(-1). The highest concentration of the individual linear siloxanes, L(9)-L(14), ranged between 2680 and 6170 ng g(-1). Concentrations of total linear siloxanes (TLS) were 1-2 orders of magnitude higher than concentrations of total cyclic siloxanes (TCS), in all indoor dust samples. Siloxane concentrations in dust were associated with the number of electrical/electronic appliances, number of occupants, and smokers living in the house. Based on the measured siloxane concentrations and on estimated daily ingestion rates of dust by toddlers and adults, we calculated the daily intake of siloxanes. For adults, daily exposure to total siloxanes, based on an average dust intake rate and median exposure concentration, was calculated to be 15.9 ng day(-1); the corresponding value for toddlers was 32.8 ng d(-1).

Survey of organosilicone compounds, including cyclic and linear siloxanes, in personal-care and household products

The determination of organosiloxanes in consumer products is important for the evaluation and characterization of sources of human and environmental exposures. In this study, we determined concentrations of cyclic siloxanes [octamethylcyclotetrasiloxane (D(4)), decamethylcyclopentasiloxane (D(5)), dodecamethylcyclohexasiloxane (D(6))], tetradecamethylcycloheptasiloxane (D(7))] and linear siloxanes (L(4) to L(14)) in a variety of consumer products (n = 76), including hair-care products, skin lotions, body washes, cosmetics, nursing nipples (i.e., pacifiers), cookware, and household sanitation products such as cleansers and furniture polishes, using gas chromatography-mass spectrometry with selected ion monitoring. Prior to the analysis of samples, a method was developed to reduce the contamination arising from organosiloxanes present in certain gas chromatograph (GC) parts, such as the inlet septum; use of a Restek BTO septum at an inlet temperature of 200 degrees C gave the lowest background level (D(4): 0.8 pg; D(5): 0.3 pg; D(6): 0.2 pg). Concentrations of cyclic siloxanes in consumer products analyzed ranged from <0.35 to 9380 microg/g, from <0.39 to 81,800 microg/g, from <0.33 to 43,100 microg/g, and from <0.42 to 846 microg/g for D(4), D(5), D(6), and D(7), respectively. Concentrations of linear siloxanes varied from <0.059 to 73,000 microg/g. More than 50% of the samples analyzed contained D(4), D(5), or D(6). Cyclic siloxanes were predominant in most of the sample categories; D(5) was predominant in hair-care products, skin lotions, and cosmetics; D(6) or D(7) was predominant in rubber products, including nipples, cookware, and sealants. Potential daily exposure to total organosiloxanes (sum of cyclic and linear siloxanes) from the use of personal-care products by adult women in the United States has been estimated to be 307 mg. Significant positive correlations (p < 0.01) existed in our study between D(4) and D(7), D(4) and linear siloxanes, D(5) and D(6), and D(5) and linear siloxanes. The correlations can be related to the composition of organosiloxanes used in consumer products. The results of our study suggest that a wide variety of consumer products that are used on a daily basis contain cyclic and linear siloxanes and these products can contribute considerably to human exposures.

Evidence for a Novel Endocrine Disruptor: The Pesticide Propanil Requires the Ovaries and Steroid Synthesis to Enhance Humoral Immunity

Steroid hormones are known to affect the humoral immune response to a variety of antigens. However, the mechanisms regulating these effects are poorly understood. The immunotoxic chemical propanil and estrogen have similar effects on the immune system including augmentation of humoral immune responses. Propanil enhances the number of phosphorylcholine (PC)-specific IgG2b, IgG3, and IgM antibody-secreting cells (ASCs) in the spleen four- to sixfold 7 days after vaccination of female C57BL/6 mice with heat-killed Streptococcus pneumoniae. Several experiments were performed to test the hypothesis that propanil increases the response via an estrogenic pathway. Ovariectomy abrogated the effect of propanil on the PC-specific ASC response. Both in vitro and in vivo assays indicate that propanil does not bind either estrogen receptor (ER) alpha or beta. Exogenous estradiol administration in ovariectomized mice failed to restore the effect of propanil on the PC response. Treatment of female mice with a pure ER antagonist, ICI 182,780, or the progesterone antagonist RU486 did not inhibit the increase in ASCs. These data suggest that estrogen and progesterone do not regulate the effect of propanil. However, complete inhibition of steroid synthesis with the gonadotropin-releasing hormone (GnRH) antagonist antide abrogated the increased response in propanil-treated mice, indicating a necessary role for steroid synthesis. Experiments in male mice demonstrated that propanil increased the number of ASCs comparable to female mice. However, orchiectomy did not inhibit this effect, suggesting that androgens do not regulate the amplification of the humoral response. These data suggest a novel role for the ovarian hormones in the regulation of the PC-specific antibody response.

Regulation of endocrine-disrupting chemicals: critical overview and deficiencies in toxicology and risk assessment for human health

Regulation of endocrine-disrupting chemicals is reviewed in terms of hazard assessment (regulatory toxicology) and risk assessment. The current range of regulatory general toxicology protocols can detect endocrine toxicity, but specific endocrine toxicology tests are required to confirm mechanisms (e.g. oestrogenic, anti-androgenic). Strategies for validating new endocrine toxicology protocols and approaches to data assessment are discussed, and deficiencies in regulatory toxicology testing (e.g. lack of adrenocortical function assessment) identified. Recent evidence of a role of prolactin in human breast cancer also highlights deficiencies in regulatory evaluation. Actual human exposure to chemicals and the high-exposure example of chemicals in body-care cosmetics is reviewed with reference to evidence that common ingredients (e.g. parabens, cyclosiloxanes) are oestrogenic. The hypothesis and epidemiology concerning chemical exposure from body-care cosmetics (moisturizers, lotions, sun screens, deodorants) and breast cancer in women is reviewed, applying Bradford-Hill criteria for association and causality, and research requirements are identified.

Environmental oestrogens, cosmetics and breast cancer

The established role of oestrogen in the development and progression of breast cancer raises questions concerning a potential contribution from the many chemicals in the environment which can enter the human breast and which have oestrogenic activity. A range of organochlorine pesticides and polychlorinated biphenyls possess oestrogen-mimicking properties and have been measured in human breast adipose tissue and in human milk. These enter the breast from varied environmental contamination of food, water and air, and due to their lipophilic properties can accumulate in breast fat. However, it is emerging that the breast is also exposed to a range of oestrogenic chemicals applied as cosmetics to the underarm and breast area. These cosmetics are left on the skin in the appropriate area, allowing a more direct dermal absorption route for breast exposure to oestrogenic chemicals and allowing absorbed chemicals to escape systemic metabolism. This review considers evidence in support of a functional role for the combined interactions of cosmetic chemicals with environmental oestrogens, pharmacological oestrogens, phyto-oestrogens and physiological oestrogens in the rising incidence of breast cancer.