Table 1.

Summary of DREAM and corresponding GuLF DREAM parameters and weightings

Parameter	Original DREAM weightings	GuLF STUDY DREAM weightings	Changes for GuLF STUDY
Intrinsic emission (substance/environmental factors)
Concentration	Value between 0 and 1 (categorical)	Value between 0 and 1 (continuous)	Entered as a continuous variable rather than categorical as this resulted in stronger correlation with measurement values in DREAM validation (Van Wendel de Joode, Vermeulen, Van Hemmen et al., 2005 and Van Wendel de Joode, Van Hemmen, Meijster et al. (2005).)
Viscosity*/emission	Low = 1 Medium =1.75 High =3	Low = 1 Medium low = 2.0 Medium = 3 Medium high = 6.0 High = 9	Increased weighting of high category to reflect increased retention with increased viscosity (Cinalli et al., 1992 and Gorman Ng et al., 2013). Intermediate levels (medium low and medium high) added to increase differentiation among GuLF STUDY participants. The effect of viscosity was attenuated when cotton clothing was used as Gorman Ng et al. (2013) found that viscosity had a limited effect on uptake by cotton materials (see supplementary materials).
Viscosity/surface transfer	Low = 1 Medium = 1.75 High = 3	Low = 1 Medium low = 1.375 Medium = 1.75 Medium high = 2.375 High = 3	No changes made. Cinalli et al., (1992) and Gorman Ng et al., (2013) found no difference in surface transfer with increasing viscosity. Intermediate levels (medium low and medium high) added to increase differentiation among GuLF STUDY participants
Viscosity/deposition	Low = 1 Medium = 1.75 High = 3	Low = 1 Medium low = 1.375 Medium = 1.75 Medium low = 1.375 High = 3	No changes made. Gorman Ng et al. (2013) found no evidence that viscosity influences exposure by deposition if air concentrations are held constant. Intermediate levels (medium low and medium high) added to increase differentiation among GuLF STUDY participants
Evaporation	<50ºC = 3 50–150ºC = 1 >150ºC = 0.3	Not included	To refine the effect of evaporation this variable was replaced by two factors that influence the rate of evaporation: vapour pressure and wind speed
Vapour pressure	Not included	<50 Pa = 1 50–100 Pa = 0.75 100–1000 Pa = 0.1 1000–10000 Pa = 0.01 >10000 Pa = 0.005	Evaluated using both IH SkinPerm and the NIOSH Skin Permeation Calculator. Both calculators showed an increasing rate of evaporation with increasing vapour pressure, as reflected in the weightings
Velocity of air	Not included	Dispersants: <1–3 mph = 1 3–10 mph = 0.75 >10 mph = 0.5 Oils and tars: any wind speed = 1	Evaluated using both IH SkinPerm and the NIOSH Skin Permeation Calculator. The weightings are based on the more conservative estimates from the NIOSH model
Exposure route factor
Exposure Route Factor	Emission = 3 Surface transfer = 1 Deposition = 1	Emission = 5 Surface transfer = 3 Deposition =1	Emission and surface transfer weightings were increased to reflect the evidence that suggests that emission results in exposures far greater than the other pathways (Gorman Ng et al., 2013), and surface transfer typically results in exposures higher than deposition (Burstyn et al., 2002; Pronk et al., 2006; Links et al., 2007)
Frequency and intensity of exposure
Frequency of exposure by emission and surface transfer	<1% of task duration = 0 <10% of task duration = 1 10–50% of task duration = 3 ≥50% of task duration = 10	<1% of task duration = 0 <10% of task duration = 1 10–50% of task duration = 3 ≥50% of task duration = 5	The weightings for the highest frequency category were reduced. Hughson and Cherrie (2003) found that skin becomes saturated following emission or surface transfer exposure. It is unlikely that there would be such a big difference between exposure for <50 and >50% of the task
Frequency of exposure by deposition	<1% of task duration = 0 <10% of task duration = 1 10–50% of task duration = 3 ≥50% of task duration = 10	<1% of task duration = 0 <10% of task duration = 1 10–50% of task duration = 3 ≥50% of task duration = 10	No change made Exposure levels from deposition are typically not high enough to result in saturation (Gorman Ng et al., 2013) so the original values have been retained
Intensity of emission or deposition exposure (amount of body part exposed)	<10% of body part = 1 10–50% of body part = 3 ≥50% of body part = 10	<10% of body part = 1 10–50% of body part = 3 ≥50% of body part = 10	No change made The available evidence suggests a linear relationship between body surface area exposed and exposure (Brouwer, Lansink et al., 2000, and Brouwer, de Vreede et al., 2000) supporting the original DREAM values
Intensity of surface transfer: contamination level of surface	Not contaminated = 0 Possibly contaminated = 1 <50% of surface = 3 ≥50% of surface = 10	Not contaminated = 0 Possibly contaminated = 1 <50% of surface = 3 ≥50% of surface = 10	No change made Brouwer et al. (1999), Cohen Hubal et al. (2005), and Christopher (2008) found a relationship between the loading of material on surfaces and the mass transferred to the skin following contact supporting the original DREAM values
Gloves and protective clothing
Glove or clothing material by body part	No glove or body part not covered = 1 Woven clothing = 0.3 Non-woven permeable = 0.1 Non-woven impermeable = 0.03	No glove or body part not covered = 1 Woven or permeable clothing or inappropriate materials = 0.9 Non-woven impermeable gloves or clothing = 0.5	The impact of gloves and clothing on exposure was reduced. The literature on glove effectiveness suggested that the original DREAM model overestimated the effect of gloves on exposure. (Scheepers et al., 2009; Weiss et al., 2011; Wang et al., 2006)
Pressure and friction on gloves	Gloves = 1 Clothing = 0.3	Not included	No evidence was found that ‘pressure or friction on gloves’ plays a role in glove effectiveness
Replacement frequency	Replaced after use = 0.3 Daily = 1 Weekly = 3 Monthly = 10	Replaced within a work shift = 0.3 Replaced daily = 1 Replaced < daily = 3	The original DREAM values may have overestimated the effect of reuse of clothing and gloves. These categories were also changed to match the GuLF STUDY questionnaire
Non-woven gloves connect well with clothing	No = 3 Yes = 1	No = 1.3 Yes = 1	The weighting was modified to reflect the lower overall protection assumed from wearing gloves. Creely and Cherrie (2001) support the importance of this factor, although there is no quantitative data to substantiate the magnitude
Non-woven gloves wear time	0–25% of time = 10 25–99% of time = 3 100% of time = 1	0–25% of the time = 2 25–99% of time = 1.2 100% of time = 1	The magnitude of the parameters was reduced based on the lower effectiveness assumed for clothing and gloves
Under gloves worn with impermeable gloves	No = 1 Yes = 0.3	Not included	No evidence was found that under gloves have any impact on exposure
Replacement frequency of under gloves	Single use = 1 Daily = 3 Weekly or monthly = 10	Not included	No evidence was found that under gloves have any impact on exposure
Barrier cream	Not used = 1 Used = 0.3	Not included	Barrier creams were not used by remediation workers in the GuLF study
Seawater	Not included	Dispersants = 1 Oils and tars = 2	This variable was added to reflect the effect of seawater exposure on dermal uptake. Exposure to water can damage the skin and can increase uptake of chemicals by a factor of up to 4 (Yoshizawa et al., 2001). The effect was not applied to dispersants as they are water soluble and would be washed away by water, counteracting the effect of increased uptake

*Low: e.g. water, centipoise = 1. Medium: e.g. sweet Louisiana (LA) crude oil, centipoise = 35–40. High viscosity: e.g. tar, centipoise = ~several thousands.