RESEARCH ARTICLE

# Environmental impacts of examination gloves made of natural rubber and nitrile rubber, identified by life-cycle assessment

Supatra Patrawoot<fnref n="1" />,<fnref n="2" />

Thierry Tran<fnref n="3" />,<fnref n="4" />

<figure><img src="image_1.png" /></figure>

Marisa Arunchaiya<fnref n="5" />

Voranuch Somsongkul<fnref n="6" />

Yusuf Chisti<fnref n="7" />

<figure><img src="image_2.png" /></figure>

Nanthiya Hansupalak<fnref n="1" />,<fnref n="2" />,<fnref n="8" />,<fnref n="9" />

<figure><img src="image_3.png" /></figure>

**Correspondence**

Nanthiya Hansupalak, Department of
Chemical Engineering, Kasetsart
University, Bangkok 10900, Thailand.
Email: fengnyh@ku.ac.th

**Funding information**

National Research Council of Thailand;
Thailand Research Fund, Grant/Award
Number: RDG5850025

**Abstract**

Medical examination gloves made of natural rubber (NR; powdered and non-powdered) and synthetic nitrile rubber (NBR) were compared in terms of their environmental impact using life cycle assessments spanning material extraction, transportation to the glove production factory, the production process, and disposal by total incineration. ReCiPe Midpoint (H) V1.13/World Recipe H life cycle assessment method implemented using the SimaPro 9.0.0.48, was used. Single scores of each glove type and stage were determined by using weighting factors specifically obtained from a 2014 survey in Thailand. With current technologies, the overall environmental impact, or the total single score, of NR gloves was higher than of NBR gloves, because the glove production stage of NR gloves required more energy and sulfur use. In addition, the overall environmental impact of both types of gloves was found to be lower if powder coating was used rather than chlorination to reduce stickiness, and if glove production relied on natural gas for energy rather than coal. The single score approach revealed the hotspots for potential improvements for each glove type.

**KEYWORDS**

glove life-cycle-analysis (LCA), glove production, latex gloves, medical gloves

<footnote n="1">¹Department of Chemical Engineering, Kasetsart University, Bangkok, Thailand</footnote>

<footnote n="2">²Center of Excellence on Petrochemical and Materials Technology, Kasetsart University, Bangkok, Thailand</footnote>

<footnote n="3">³Qualisud/ELSA Group, Université Montpellier, CIRAD, Institut Agro, Université d'Avignon, Université de La Réunion, Montpellier, France</footnote>

<footnote n="4">⁴Alliance of Biodiversity International and the International Center for Tropical Agriculture (CIAT), Cali, Colombia</footnote>

<footnote n="5">⁵Department of Materials Science, Kasetsart University, Bangkok, Thailand</footnote>

<footnote n="6">⁶Department of Industrial Chemistry, King Mongkut's University of Technology North Bangkok, Bangkok, Thailand</footnote>

<footnote n="7">⁷School of Engineering, Massey University, Palmerston North, New Zealand</footnote>

<footnote n="8">⁸Center for Advanced Studies in Industrial Technology, Kasetsart University, Bangkok, Thailand</footnote>

<footnote n="9">⁹Specialized Center of Rubber and Polymer Materials for Agriculture and Industry, Kasetsart University, Bangkok, Thailand</footnote>
1 | INTRODUCTION

Examination gloves are widely used in healthcare facili-
ties, laboratories, food factories, and diverse other busi-
nesses. Such gloves are designed for single use and
disposal to prevent transmission of infection. The global
demand for these gloves was around US$6 billion in 2019
and is expected to grow at a compounded annual rate of
10.6%–11.2% until 2027 at least. The largest markets for
examination gloves are North America and Europe.[1,2]
The examination gloves used worldwide are produced
from either natural rubber (NR) or synthetic rubber
(e.g., nitrile, vinyl, and neoprene rubbers). NR is the
dominant material for producing gloves, followed by
nitrile rubber. These two materials are forecast to domi-
nate the global market for the foreseeable future.[1]

Irrespective of the type of rubber used in their pro-
duction, examination gloves are available with and with-
out an internal powder coating of cornstarch. Powder
acts as a lubricant making coated gloves easier to put on
and remove. The powder also absorbs sweat, providing a
comfortable feel to the user,[3] although the use of pow-
dered gloves in medical facilities has been banned in sev-
eral countries (e.g., USA, Germany, Philippines, Japan,
and Saudi Arabia) because of concerns relating to con-
tamination and allergenic reactions in patients. This has
increased the demand for powder-free gloves. The
powder-free gloves are produced by two different
methods, either chlorination or polymer coating.[4] The
chlorination process usually involves multiple washings
of the powdered gloves with a solution of hypochlorite
and hydrochloric acid. During washing, the surface of the
rubber film is oxidized, decreasing friction, or tackiness
of the surface. In the alternative polymer coating method
of reducing surface stickiness, a polymer (e.g., acrylic
polyurethane, and silicone polymers) is used to coat
inner surface of the gloves,[3,4] and this may be followed
by chlorination.

Although NR examination gloves presently dominate
the global market and are expected to retain this domi-
nance at least in the near term,[1] the use of nitrile gloves
is growing rapidly. This preference for nitrile gloves is
driven by the presence of potentially allergenic proteins
on the surface of NR gloves.[5,6] These proteins occur nat-
urally in the latex harvested from the rubber tree and can
be removed with additional processing.[5,6] Allergenicity
notwithstanding, NR gloves have superior barrier prop-
erty, elasticity, resistance to sharp objects, and strength
than nitrile gloves[4,7] and are preferred in many
applications.

In addition to performance and price, the consumer
preference is increasingly influenced also by the environ-
mental impact of a product. Consequently, environmental

impacts are being assessed and used in product market-
ing. Environmental impact of a product can be calcu-
lated using a cradle-to-grave life cycle assessment (LCA).
LCA is an environmental management tool that
evaluates inputs, outputs, and potential environmental
impacts associated with a product during its entire life
cycle.[8,9]

Although separate LCA of NR gloves and nitrile
gloves have been used to assess their environmental
impacts,[10,11] the specific types (e.g., medical examina-
tion, food processing, or industrial grade) of gloves used
in these evaluations were not specified.[10,11] LCA is
affected by the glove type because, depending on
intended application, their production requires different
amounts of raw materials (e.g., rubber and other
chemicals) and energy. Furthermore, earlier LCAs used
dissimilar functional units and focused on different envi-
ronmental impacts. Consequently, the environmental
performance of NR and nitrile gloves cannot be quantita-
tively compared based on the available reports.[10,11] The
present study fills this gap.

The present work assesses midpoint environmental impacts of NR examination gloves (powdered and powder-free) and powder-free nitrile examination gloves using a LCA spanning the extraction of the raw materials and energy, the production process, and disposal of the used gloves. The actual use stage of the glove was excluded from LCA as there were no inputs or emissions associated with it. ReCiPe Midpoint (H) V1.13/World Recipe H method and the SimaPro 9.0.0.48 software were used for the characterization and normalization steps. To provide multiple criteria for decision-making, all midpoint environmental impacts were aggregated into a single score by using weighting factors established by a survey conducted in Thailand in 2014.[12] Process-related data were collected on-site from two glove manufacturers in Thailand. The data obtained enabled a robust comparison of the environmental impacts of NR and nitrile examination gloves and of powdered and powder-free NR gloves. Medical examination gloves referred to simply as ‘gloves’ in the remainder of this work, were the specific focus of this study. Hotspots of environmental impact were identified and options were explored for reducing these impacts.

2 | MATERIALS AND METHODS

2.1 | The methodological approach

LCA comprised of the following four phases: Goal and
scope definition, the life cycle inventory (LCI) analysis,
environmental impact assessment, and interpretation.[8,13]
The environmental impacts calculations were conducted using the ReCiPe Midpoint (H) V1.13/World Recipe H methods and SimaPro 9.0.0.48 software (www. simapro.com).

## 2.2 | Goal, scope and system boundaries

The goals of the study were to evaluate cradle-to-grave environmental impacts of: (1) Four glove types produced at two factories; and (2) switching from coal to natural gas in production of NR and nitrile gloves. The glove types evaluated were: (1) Powder-free nitrile gloves produced at Factory 1 (NBRPF1); (2) powder-free NR gloves produced at Factory 1 (NR PF1); (3) powder coated NR gloves produced at Factory 2 (NR PP2); and powder-free NR gloves produced at Factory 2 (NR PF2). The powder coating material was corn starch in all cases. For comparison of different products, all data were normalized to a common basis of a functional unit (FU) of 100 pieces of gloves.

The relevant processes and systems boundaries are shown in Figure 1. The production technologies and

processes for NR gloves at the two factories were different, as summarized in Figure 1 (see caption). Route 1 (marked on the flow diagram in the orange box; Figure 1) was the production path of NR PF1 and NBR PF1 at Factory 1, whereas at Factory 2, Routes 2 and 3 applied to NR PP2 and NR PF2, respectively. The system boundaries of all four glove types included the transportation of materials to a glove factory, glove production, and disposal (Figure 1). For production of raw materials, two cases were considered: (1) For nitrile gloves, the system boundaries included production of raw materials (acrylonitrile butadiene rubber latex, or nitrile latex for short), based on Ecoinvent LCI of acrylonitrile, butadiene, and styrene[¹⁴]; and (2) for NR gloves, the system boundaries included the agricultural production of fresh NR latex (dry rubber content, or DRC, of 30%) and production of concentrated NR latex with 60% DRC (Figure 1).

Furthermore, after vulcanizing and cooling steps, the production routes for NR PF1, NR PF2, and NR PP2 were different as shown by the numbered arrows in Figure 1 (orange box). NR PF1 underwent the polymer

<figure><img src="image_4.png" /><figcaption>**FIGURE 1** The common system boundaries for all four gloves comprised the glove production and disposal processes. For natural rubber (NR) gloves, the system boundaries for agricultural production of NR latex and production of concentrated NR latex were added. Route 1 (marked on flow diagram in the orange box) was the production path of powder-free NR gloves from Factory 1 (NR PF1) and powder-free nitrile gloves from Factory 1 (NBR PF1), whereas Routes 2 and 3 were of powder coated NR gloves from Factory 2 (NR PP2) and powder-free NR gloves from Factory 2 (NR PF2), respectively. Dashed lines specify boundaries for rubber plantation, concentrated NR latex factory, glove factory, and the used glove disposal operation</figcaption></figure>
coating and chlorination treatments before drying, strip-
ping, inspection, and packaging (Route 1, Figure 1),
whereas NR_PP2 and NR2 underwent powder dip-
ping together (Route 2, Figure 1). However, after being
stripped from the forming molds (or formers; Figure 1),
only NR_PP2 went straight for inspection and packaging,
whereas NR PF2 went to chlorination treatment (Route
3, Figure 1). Finally, the production route for NBR PF1
was nearly identical to that of NR PF1, except that the
gloves underwent chlorination only, without polymer
coating.

The disposal stage took into account only the waste
gloves (excluding packaging boxes because they could be
recycled). Disposal was by incineration, a common prac-
tice for used medical gloves.[11] The impacts of infrastruc-
tures (factory buildings, machinery) were not included in
this analysis as their contributions were deemed insignifi-
cant in relation to the materials and energy consumed
during the 20-25 years lifetime of a factory.

## 2.3 | Life cycle inventory

Inputs and outputs for each system boundary were calcu-
lated for 1-year of production of gloves and were then
normalized to a FU of 100 pieces of gloves. The input-
output data for glove production were collected via onsite
interviews with staff of the two factories. LCI of the four
glove types were proprietary and protected by confidenti-
ality agreements with the two factories involved, but life
cycle inventories for similar products have been reported
elsewhere.[10,11]

The input-output data for agricultural production of
fresh NR latex and production of concentrated NR latex
were retrieved from Thai National Life Cycle Inventory
Database.[15] The LCI of production and concentration of
fresh NR latex are confidential, but LCI data for similar
products are available in the literature.[11]

LCI of acrylonitrile butadiene rubber latex, or nitrile
latex, was not available in Thai National Life Cycle
Inventory Database,[15] but the major components of
nitrile latex (i.e., acrylonitrile and butadiene) are similar
to those of ABS (acrylonitrile butadiene styrene) plastic.
Therefore, the LCI of nitrile rubber was estimated by
excluding styrene from the LCI of ABS retrieved from
Thai National Life Cycle Inventory Database.[15]

Generic data (e.g., transportation vehicles, chemicals)
were retrieved from Ecoinvent (www.ecoinvent.org). All
chemicals and packaging used in the glove production,
except latexes, were assumed to be transported from cen-
tral Bangkok to each glove factory. Both NR and nitrile
rubber latexes came from provinces located near the two
factories.

Factory 1 produced powder-free NR gloves and powder-free nitrile gloves by using the same production lines, but at different times. Similarly, Factory 2 produced powder-free NR gloves and powdered NR gloves by using the same production lines, but at different times. The data on water and energy (electricity and fuel) use of each factory were based on the monthly bills for the year of data collection. As the factories did not record water and energy use separately for each type of glove, these data were estimated for each factory based on its total consumption and the quantities (number of pieces) of each glove type it produced in the year of LCI collection.

The process wastewater in each factory was screened
to remove rubber scrap and then released into an open
biological treatment lagoon. The treatment involved
anaerobic fermentation of the organic matter and released
methane and carbon dioxide gases into the atmosphere.

The treated water from Factory 1 was fed to a water
spraying system to improve dust control in the coal work-
ing area. During spraying, some water evaporated and
some percolated into the ground. The quantity of water
seeping into the ground and any pollutants it may have
leached from the coal dust into the soil, could not be
evaluated reliably. In addition to the water seeping into
the earth, water also left the system boundary as vapor
during drying processes and other activities in the fac-
tory. As the compositions in the water leaving the system
boundary were not known, the water discharge data cell
in SimaPro was left blank, implying no environmental
contribution from the water discharged.

After treatment, the water discharged from Factory
2 had a chemical oxygen demand within the regulatory
norms for such factories in Thailand, and was released to
a natural water source outside the factory boundary.
There was no metered record of water discharge and
therefore it was taken to be 50% of the water entering the
factory perimeter. Thus, the remaining 50% of the input
water left the boundary as vapor from drying processes,
as was the case in Factory 1.

The solid waste in both factories was the gloves that
failed quality tests and rubber scrap retrieved from the
wastewater. The solid waste was sold to a third party who
burnt it to recuperate heat for other processes. Thus, the
total environmental impact of the glove production had
to be divided, or allocated, to the gloves passing the qual-
ity tests and those in the solid waste. The allocation of
environmental impacts between the product and the
waste was performed on a mass basis. The mass of waste
gloves in each factory was approximated to be 3% of the
total mass of gloves produced per year. Thus, the gloves
passing the quality tests were assigned 97% of the total
environmental impact and the waste gloves were
assigned 3% of the total environmental impact.
Emissions to air from the glove factories were mainly a consequence of the fuel burnt. Factory 1 burnt coal while Factory 2 used natural gas. In addition, there were emissions (CH₄ and CO₂) from open wastewater treatment lagoons at both factories.

Waste gloves in this study were treated as infectious waste. Such waste can be disposed by incineration, or other methods.[16] The ash produced is handled as if it were municipal solid waste.[16] For disposal of infectious waste by methods other than incineration, additional tests are required to demonstrate destruction of pathogens. Hence, in Thailand waste medical gloves are mostly disposed by incineration.[11]

In a typical incinerator,[17] the waste is burnt in two consecutive stages. In the first stage, the waste is pyrolyzed at 760–980°C under oxygen-limiting conditions. This dries the waste and decompose it to volatile gases and ash. The volatile gases formed in the first stage are burnt in the second stage at 980–1095°C with excess air to achieve complete combustion. The ash produced is disposed in landfills like most municipal solid waste.[16]

For this study, incineration was assumed to result in complete combustion of waste gloves. Elemental analysis (CHNS/O analyzer; Thermo Scientific™ FLASH 2000), thermogravimetric analysis (TGA/DSC1; Mettler Toledo) and scanning electron microscopy (Quanta 450 SEM with Energy Dispersive X-Ray Analysis; FEI) were used to determine the compositions of all four glove types under study. Based on the experimentally determined elemental compositions, the assumption of complete combustion and stoichiometric considerations,[18] emissions to atmosphere and the ash production were estimated. Ash is potentially recyclable and recycling reduces its environmental impact.[19] Therefore, any environmental impact of disposing ash from glove incineration, was disregarded. In addition, environmental contributions of the fuel used in starting up the incinerator were neglected because combustion of rubber gloves is self-sustaining, that is, little or no fuel is required once combustion begins.

## 2.4 | Impact assessment

The LCI of all activities for a FU of 100 pieces of gloves produced in any factory was converted to 18 environmental impact indicators based on ReCiPe Midpoint (H) V1.13/World Recipe H (Table 1). This LCI included contributions from the rubber plantation, production of the concentrated NR latex (Figure 1) and final disposal of the used gloves.

To assist decision makers and other users of environmental impact studies, all 18 environmental impact indicators (Table 1) were normalized and combined into a

single score based on weighting factors. Normalization of the environmental impacts involved the calculation of the magnitude of a category indicator relative to some reference information (e.g., the average yearly emission, or consumption by one individual in a reference area). The value of each impact indicator was divided by a corresponding normalization factor to generate a dimensionless number for each of the 18 environmental impact categories. The resulting set of dimensionless values was then multiplied by a set of weighting factors. The weighting factors prioritized impact categories from those of highest concern to those of lowest concern, as perceived by the people in the geographic region of focus. Finally, all 18 weighted dimensionless impact values were aggregated into a single score for a product or a service.[20,21] The following equation was used in calculating the single score (point, Pt) of a system boundary:

$$ \text{Single score (Pt)} = W_1 \left(\frac{V_1}{F_1}\right) + W_2 \left(\frac{V_2}{F_2}\right) + \dots + W_{18} \left(\frac{V_{18}}{F_{18}}\right), \quad (1) $$

<table><caption>**TABLE 1** Environmental impact indicators, the corresponding acronyms and units</caption><thead><tr><th>Impact category</th><th>Acronym</th><th>Units</th></tr></thead><tbody><tr><td>Climate change</td><td>CC</td><td>kg CO<sub>2</sub> eq</td></tr><tr><td>Ozone depletion</td><td>OD</td><td>kg CFC-11<br>eq</td></tr><tr><td>Terrestrial acidification</td><td>TA</td><td>kg SO<sub>2</sub> eq</td></tr><tr><td>Freshwater eutrophication</td><td>FE</td><td>kg P eq</td></tr><tr><td>Marine eutrophication</td><td>ME</td><td>kg N eq</td></tr><tr><td>Human toxicity</td><td>HT</td><td>kg 1,4-DB eq</td></tr><tr><td>Photochemical oxidant<br>formation</td><td>POF</td><td>kg NMVOC</td></tr><tr><td>Particulate matter formation</td><td>PMF</td><td>kg PM<sub>10</sub> eq</td></tr><tr><td>Terrestrial ecotoxicity</td><td>TET</td><td>kg 1,4-DB eq</td></tr><tr><td>Freshwater ecotoxicity</td><td>FET</td><td>kg 1,4-DB eq</td></tr><tr><td>Marine ecotoxicity</td><td>MET</td><td>kg 1,4-DB eq</td></tr><tr><td>Ionizing radiation</td><td>IR</td><td> kBq U<sup>235</sup> eq</td></tr><tr><td>Agricultural land occupation</td><td>ALO</td><td>m<sup>2</sup> a</td></tr><tr><td>Urban land occupation</td><td>ULO</td><td>m<sup>2</sup> a</td></tr><tr><td>Natural land transformation</td><td>NLT</td><td>m<sup>2</sup></td></tr><tr><td>Water depletion</td><td>WD</td><td>m<sup>3</sup></td></tr><tr><td>Metal depletion</td><td>MRD</td><td>kg Fe eq</td></tr><tr><td>Fossil depletion</td><td>FD</td><td>kg oil eq</td></tr></tbody></table>

Note: Based on ReCiPe Midpoint (H) V1.13/World Recipe H.
Abbreviations: CFC, chlorofluorocarbons; 1,4-DB, 1,4-dichlorobenzene; NMVCO, non-methane volatile organic compounds; PM₁₀, particulate matter with diameter < 10 µm.
where $V_i$ was the total value of the environmental impact category i contributed by all activities in a system boundary, $F_i$ was the normalization factor for the impact category i, and $W_i$ was the weighting factor associated with the impact category i.

In the present work, all computations of environmental impact category values and normalization were carried out using the SimaPro 9.0.0.48 with ReCiPe Midpoint (H) V1.13/World Recipe H. Single scores were determined manually. The weighting factors were from a 2014 survey of the environmental concerns and priorities of the respondents.[12]

# 3 | RESULTS AND DISCUSSION

## 3.1 | Characterization results

A common observation for all four glove types was that the glove production stage contributed the most (>50%) to the impact categories CC, OD, FE, ME, HT, POF, TET, FET, MET, IR, ALO, ULO, NLT, WD, MRD, and FD for 1 FU of gloves produced (Figures 2(A)–(D)). Further

investigation revealed (Figure 3) that for most of these environmental impact categories, fuel production and use contributed the most (>50%) to the glove types NR_PF1 and NBR_PF1. Fuel production and use contributed the most (>50%) also to the glove types NR_PF2 and NR_PP2, but in fewer impact categories compared to the glove types NR_PF1 and NBR_PF1. This could be ascertained simply by counting the number of impact categories in Figures 3(A)–(D) for the different glove types. These results implied that coal production and burning contributed a greater environmental impact compared with the use of natural gas as fuel. As a consequence, when natural gas was used, the environmental impact contributions of the other activities were made apparent through magnification in relative terms. Fuel, or heating requirements, has been found to contribute the most to environmental impacts also in other studies of glove production.[10] In glove production processes, coal and gas are used to mainly generate heat for warming liquid latexes, drying and chlorination.

Production of concentrated latex (i.e., NR and nitrile latexes) and transportation of materials to the glove factory also contributed to environmental burdens, but their

<figure><img src="image_5.png" /><figcaption>**FIGURE 2** The total characterization results for production of one functional unit (FU) of gloves, shown as percentage contribution. “Concentrated latex” means natural rubber (NR) concentrated latex used in making NR gloves (Figures 2(A), (C), (D)), and nitrile latex used in making nitrile gloves (Figure 2(B)). See Table 1 for explanation of the acronyms shown below the bars. Glove types: Powder-free NR gloves from Factory 1 (NR_PF1); powder-free nitrile gloves from Factory 1 (NBR_PF1); powder-free NR gloves from Factory 2 (NR_PF2); powder coated NR gloves from Factory 2 (NR_PP2)</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**FIGURE 3** The total characterization results, classified by activities within the glove factories per 1 FU of gloves, shown as percentage contribution. To enable comparison with nitrile rubber (NBR), the environmental impacts for both latexes were evaluated by using a cradle-to-gate approach. Thus, the environmental impacts of production of the concentrated natural rubber (NR) latex were the sum of the impacts from the production of fresh NR latex and those of concentrated NR latex. “Concentrated latex” means NR concentrated latex (includes production of fresh NR latex) for NR gloves (Figures 3(A), (C), (D)), and nitrile latex for nitrile gloves (Figure 3(B)). See Table 1 for explanation of the acronyms shown below the bars. See caption of Figure 2 for explanation of glove types</figcaption></figure>

impact was relatively small in the glove production stage (Figures 2(A)–(D)). The environmental impacts of production of concentrated NR latex in Figures 2(A), (C), and (D) were assessed using a gate-to-gate approach. Thus, these impacts included both activities inside and outside the factory. The activities outside the factory (i.e., outside the latex production stage) were those relating to production of chemicals, water, and energy (fuel and electricity), but excluding the activities involved in the production of fresh NR latex. The environmental impacts of the production of fresh NR latex were separately determined using a cradle-to-gate approach, accounting for all activities involved outside the plantation boundary relating to all materials, water, and energy that entered the plantation, as well as all activities occurring within the plantation. In contrast to the gate-to-gate approach used for assessing impacts of production of

concentrated NR latex, the impacts of production of nitrile latex were determined using a cradle-to-gate approach. This took into account all activities relating to materials, water, and energy that went into the latex production stage and all activities occurring within the latex production stage.

A comparison of all 18 impact categories for the four glove types (Figure 4) revealed that NR_PP2 contributed the least to nearly all environmental impact categories except OD, that is, the emissions related to depletion of ozone.

## 3.2 | Single score results

Different individual impact categories often have different units (Table 1) and therefore cannot be compared. To
simplify comparison of overall impact, the impact category results from the previous section were aggregated into a single score. This score represented the overall environmental impact of a glove type as perceived by the survey respondents. This single-score approach allowed easy identification of the glove type with the least overall environmental impact and recognition of production stages with high overall impacts.

The glove type NR_PF1 was found to have the highest weighted contribution to the overall environmental impacts, followed by NBR_PF1, NR_PF2, and NR_PP2, respectively (Figure 5(A)). For all glove types, the glove production stage had the highest contribution to the overall environmental impacts (>50%) (Figure 5(A)). This dominant impact of the production stage for glove types NR_PF1, NBR_PF1 and NR_PF2 was linked to their fuel use (production and consumption of fuel; see table in Figure 5(B)). In contrast, the high impact of the production stage of glove type NR_PP2 was linked to the chemicals used (see table in Figure 5(B)).

## 3.3 | Effect of substituting coal for natural gas in Factory 1 on the overall environmental impact

This study of fuel substitution was conducted to ascertain the impact of replacing coal with natural gas on an energy equivalent basis, without any other change to the glove production technology. Thus, the quantity of Grade G coal (calorific value = 10,048 kJ/kg[22]) required by the production processes was calculated and replaced with a quantity of natural gas (calorific value = 52,200 kJ/kg) that provided the same total energy. The recalculation of single scores revealed that the fuel substitution reduced the single scores of both NR_PF1 and NBR_PF1 gloves by more than 50% (Figure 6), bringing them closer to the levels of environmental impacts of gloves produced in Factory 2.

## 3.4 | Comparison of gloves

### 3.4.1 | NR gloves (NR_PF1) versus NBR gloves (NBR_PF1)

A comparison of each impact category for NR_PF1 and NBR_PF1 for the same functional unit (Figure 4) showed higher values for NR_PF1 in all impact categories except MRD. In terms of the overall impact, NR_PF1 had higher weighted contribution to the overall environmental impacts than NBR_PF1 (Figures 5(A)). Figure 5(B) revealed higher single scores for chemicals, production and combustion of fuel, and glove disposal stage for NR_PF1 than NBR_PF1. As both NR_PF1 and NBR_PF1 were produced by using the same technology and production process, the greater environmental impact of NR_PF1 was directly related to the different rubber latex types (i.e., NR and nitrile latexes). A change in latex type from NR to nitrile, or vice versa, affected the types and quantities of the chemicals needed for glove production. A LCA revealed that use of nitrile latex reduced the energy required for drying the glove and the sulfur required for vulcanization. Therefore, NBR_PF1 released less sulfur dioxide (SO₂) in the disposal stages than NR_PF1. This was confirmed by the low contribution of the disposal stage of NBR_PF1 for the category TA (Table 1), which was mainly influenced by the atmospheric release of SO₂. Nitrogen oxides (NOₓ), ammonia (NH₃), and hydrochloric acid (HCl) also contributed to TA, but less than SO₂.[23]

The production of nitrile latex was another important contributor to the total single score of NBR_PF1 (Figure 5(B)). The single score for the nitrile latex production was noticeably high compared to the single scores associated with the production of fresh NR latex and its concentrated form. As the nitrile latex was produced from petroleum, its production contributed greatly to the impact category fossil depletion (FD), and the residual chemicals from its decomposition could

<figure><img src="image_7.png" /><figcaption>**FIGURE 4** The total characterization results per one functional unit (FU) of gloves. See Table 1 for explanation of the acronyms shown below the bars. See caption of Figure 2 for explanation of glove types</figcaption></figure>
**FIGURE 5** Single scores (millipoint, mPt) for four glove types, based on production of 1 functional unit (FU) of gloves, classified by boundaries (A) and activities (B). “Concentrated latex” in the legend of Figure 5(A) means natural rubber (NR) concentrated latex (excluding production of fresh NR latex) for NR gloves, and nitrile latex for nitrile gloves. Numbers 1–9 below the vertical bars in Figure 5 (B) denote: (1) production of fresh NR latex; (2) production of concentrated latex; (3) transportation of materials to a glove factory; (4) chemicals; (5) packaging; (6) production and combustion of the fuel used; (7) electricity; (8) wastewater; and (9) disposal of waste gloves. The data under Figure 5(B) are single scores of each activity for specified glove types. See caption of Figure 2 for explanation of glove types

<figure><img src="image_8.png" /></figure>

contaminate soil, enhancing its impact in category TA (Figure 2(B)).[24] The main contribution of fresh NR latex to environmental impacts was in category ME (Figures 2 (A), (C), (D)). ME related to eutrophication of marine environment (i.e., excessive growth of algae and marine plants) caused by excess inputs of inorganic nutrients such as nitrates from fertilizers to the marine ecosystem.[25] Eutrophication is linked to leaching of nitrates from the rubber plantations to rivers and then to the marine environment. Nitrate is also contributed by the atmospheric release of NOₓ from nitrogen fertilizers used, and the diesel burnt, at the plantation. In the atmosphere, natural processes convert NOₓ to nitrate which ultimately rains back to Earth, to upset the nitrogen balance in water bodies and other ecosystems.[26] Although the NOₓ emissions were on land, SimaPro 9.0.0.48 accounted for their impact on the marine ecosystem.

### 3.4.2 | Powder-free NR gloves (NR_PF2) versus powdered NR gloves (NR_PP2)

Comparisons of equal functional units of NR_PF2 and NR_PP2 for individual impact categories and the overall impact showed higher values for NR_PF2 in all impact categories (Figure 4) and in single scores (Figure 5(B)). The single scores of production of fresh NR latex and of concentrated latex were identical for both glove types because identical technologies applied to latex production and concentration for both glove types. Thus, the greater environmental impact of NR_PF2 was directly related to the additional chlorination and drying processes applied to NR_PP2 in order to produce NR_PF2, as displayed in Figure 1. Life-cycle analysis based on the collected data showed that the chlorination process was the direct cause of higher single scores of chemicals and the glove
<figure><img src="image_9.png" /><figcaption>**FIGURE 6** Effect of replacing coal with natural gas (NG) in the glove production stage of powder-free natural rubber (NR) gloves from Factory 1 (NR_PF1) and powder-free nitrile gloves from Factory 1 (NBR_PF1), based on production of 1 FU of gloves. The single scores (millipoint, mPt) of concentrated latex were determined by using cradle-to-gate approach. “Concentrated latex (cradle-to-gate)” means NR concentrated latex (including fresh NR latex production) for NR gloves, and nitrile latex for nitrile gloves. See caption of Figure 2 for explanation of glove types</figcaption></figure>

disposal stage. The drying process after the chlorination treatment increased the energy use by a factor of 1.5 and hence, was the cause of a higher single score related to the production and combustion of the fuel.

### 3.4.3 | Comparison of technologies of powder-free glove production

NR_PF1 and NR_PF2 represented two technologies of producing powder-free gloves. Their production used different fuels and chemicals. To produce one FU (100 pairs of gloves), much higher values for NR_PF1 were observed in all impact categories, except OD emissions (Figure 4) and in most single scores (table in Figure 5 (B)). This was because the NR_PF1 technology used coal as a fuel (Figures 2, 3) and more sulfur was used in the vulcanization step. The significantly higher OD emissions of NR_PF2, compared to NR_PF1 (Figure 4), were linked to the use of natural gas in the glove production processes of NR_PF2 (Figures 2, 3). In addition, the higher sulfur contained in NR_PF1 led to its higher single score at the glove disposal stage compared to NR_PF2 (Figure 5(B)).

### 3.4.4 | Hotspots for each glove type

Comparison of all four glove types by using the single-score approach revealed certain environmental impact hotspots for each glove type. These are summarized in Table 2 for possible use in future mitigation through redesign of the production processes. Overall, the

<table><caption>**TABLE 2** Summary of top three environmental impact hotspots for each glove type, based on production of 1 FU of gloves</caption><thead><tr><td>Glove type<sup>a</sup></td><td>Hotspots<sup>b</sup></td></tr></thead><tbody><tr><td>NR_PF1</td><td>Fuel production and combustion > Chemicals > Glove disposal</td></tr><tr><td>NBR_PF1</td><td>Fuel production and combustion > Chemicals > Nitrile latex</td></tr><tr><td>NR_PF2</td><td>Fuel production and combustion > Chemicals > Electricity</td></tr><tr><td>NR_PP2</td><td>Chemicals > Fuel production and combustion > Packaging</td></tr></tbody></table>

production stage was the main contributor to environmental impacts. In keeping with the present study, the dominant contribution of the production stage to the environmental impacts of rubber gloves was also reported by others.[11] A significant environmental impact of the chemicals used during the production stage has also been highlighted.[11]

The type of fuel used had a major influence on environmental impacts, with coal contributing to several of the identified hotspots. As shown in Figure 6, replacing coal with natural gas had the potential to lower the overall impact by more than 50%. A fuel change from coal to natural gas may be easily implemented in existing production process. Yet, the overall environmental impacts of NR_PF1 and NBR_PF1 were still higher than NR_PF2 and NR_PP2, with the latter being the lowest among all four glove types (Figures 5(A) and 6). After fuel substitution, the replacement of chemicals used in the production stages of NR_PF1 and NBR_PF1 became the next environmental impact hotspot issue (Table 2), followed by development of a lower sulfur formula for NR_PF1 (to reduce the impact of the disposal stage) and similar improvements to production of nitrile latex for NBR_PF1.

Furthermore, the environmental impact of glove types NR_PP2 and NR_PF2 can potentially be reduced by identifying alternative chemicals with lower impacts. Minimization of natural gas use in the drying process for NR_PF2 is also important.

## 4 | CONCLUSION

The life cycles of NR and nitrile gloves (powdered and powder-free gloves) produced in two factories in Thailand were compared using a cradle-to-grave life cycle analysis approach for identical FU (100 pieces of gloves).

<footnote><sup>a</sup>Powder-free NR gloves from Factory 1 (NR_PF1); powder-free nitrile gloves from Factory 1 (NBR_PF1); powder-free NR gloves from Factory 2 (NR_PF2); powder coated NR gloves from Factory 2 (NR_PP2).</footnote>

<footnote><sup>b</sup>In descending order of single scores.</footnote>
The assessment revealed that with current technologies of glove production, regardless of whether powdered or powder-free gloves are produced, the glove production stage dominated the environmental impacts. At the raw materials stage, the nitrile latex contributed to the environmental impacts more than the NR latex, but at the production stage nitrile gloves consumed less energy and less sulfur for vulcanization. This led to a lower overall environmental impact, or the total single score, of the nitrile gloves than the NR gloves. Furthermore, a comparison of the powder-free NR gloves and powdered NR gloves showed that the chlorination process with its requirement of additional drying, energy and chemicals, increased the overall environmental impact of powder-free NR gloves. In addition, the glove-production technology using coal as fuel was found to contribute more to the environmental impacts than the technology that used natural gas. While NR gloves had higher overall environmental impact than nitrile gloves, the difference was relatively small (10%-20%). The NR gloves had the benefit of using renewable resources.

Life cycle environmental impact of a glove is but one factor that influences customer choice, usually only if the other key functional attributes of the available products are equally satisfactory. For gloves, properties such as puncture and tear resistance, stretchiness, and barrier properties, are other important considerations.

## ACKNOWLEDGMENTS

Financial support for research was provided by Thailand Research Fund (RDG5850025). Financial support for publication was provided by National Research Council of Thailand (NRCT).

## CONFLICT OF INTEREST

None to declare.

## ORCID

Thierry Tran https://orcid.org/0000-0002-9557-3340

Yusuf Chisti https://orcid.org/0000-0002-0826-7012

Nanthiya Hansupalak https://orcid.org/0000-0002-9917-403X

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**How to cite this article:** Patrawoot S, Tran T, Arunchaiya M, Somsongkul V, Chisti Y, Hansupalak N. Environmental impacts of examination gloves made of natural rubber and nitrile rubber, identified by life-cycle assessment. *SPE Polymers*. 2021;2:179–190. https://doi.org/10.1002/pls2.10036