Intervention studies to reduce the impact of climate change on health in rural communities in the United States: a systematic review

Climate change, the greatest public health threat of the 21st century, will uniquely affect rural areas that are geographically isolated and experience greater health inequities. This systematic review describes and evaluates interventions to lessen the effects of climate change on human health in the rural United States, including interventions on air pollution, vector ecology, water quality, severe weather, extreme heat, allergens, and water and food supply. Searches were constructed based on the eight domains of the Centers for Disease Control and Prevention (CDC) Framework “Impact of Climate Change on Human Health.” Searches were conducted in EBSCO Environment Complete, EBSCO GreenFILE, Embase.com, MEDLINE via PubMed, and Web of Science. Duplicate citations were removed, abstracts were screened for initial inclusion, and full texts were screened for final inclusion. Pertinent data were extracted and synthesized across the eight domains. Article quality was assessed using the Mixed Methods Appraisal Tool. Of 8471 studies screened, 297 were identified for full text review, and a total 49 studies were included in this review. Across the domains, 34 unique interventions addressed health outcomes due to air pollution (n = 8), changes in vector ecology (n = 6), water quality (n = 5), severe weather (n = 3), extreme heat (n = 2) increasing allergens (n = 1), water and food supply (n = 1), and across multiple CDC domains (n = 8). Participatory action research methodology was commonly used and strived to mobilize/empower communities to tackle climate change. Our review identified three randomized controlled trials, with two of these three published in the last five years. While original research on the impact of climate change on health has increased in the past decade, randomized control trials may not be ethical, cost effective, or feasible. There is a need for time-efficient and high-quality scholarship that investigates intervention efficacy and effectiveness for reducing health impacts of climate change upon rural populations.

. Impact of climate change on human health framework. The Centers for Disease Control (CDC) created this framework that delineates the health disruptions that arise from climate change events. Centers of Disease Control and Prevention. Climate Effects on Health. Published 3 March 2021. Accessed 6 February 2023. www.cdc.gov/climateandhealth/effects/default.htm Reproduced from CDC. CC BY 3.0.

Search strategy and information sources
A comprehensive literature search was undertaken to identify relevant published studies meeting the inclusion and exclusion criteria. The search strategies were developed and conducted by an experienced medical librarian (SL) with input from the research team. The CDC Impact of Climate Change on Human Health framework was used as the basis for design of the search strategy and the visual representation of the framework is presented in figure 1 [1]. The CDC, through its Climate and Health Program, created this framework that delineates the health disruptions that arise from climate change events. Because the CDC is one of the leading US governmental agencies that support programs to strengthen climate change adaptation programs at the local, state, and federal level, a comprehensive framework such as this is a useful tool for organizing the search terms for this systematic review. The CDC framework is divided into four sections identified as major disruptions from climate change: increasing CO 2 levels, rising sea levels, extreme weather, and rising temperatures. The framework further divides these disruptions into eight specific categories: extreme heat, severe weather, air pollution, changes in vector ecology, increasing allergens, water quality impacts, water and food supply impacts, and environmental degradation. Within the framework, each of the domains highlights potential health outcomes of interest. Extreme heat is associated with heat related illness and death and cardiovascular failure; severe weather is associated with injuries, fatalities, and mental health impacts; air pollution is associated with asthma and cardiovascular disease; changes in vector ecology is associated with multiple disease causing pathogens; increasing allergens is associated with the health impacts of respiratory allergies and asthma; water quality impacts is associated with waterborne illnesses and the negative effects of algal blooms; water and food supply impacts is associated with malnutrition and diarrheal diseases; and environmental degradation is associated with the negative mental health impacts stemming from forced migration and civil conflict.
The database searches used controlled vocabulary supplemented with keywords related to the concepts of climate change (e.g. greenhouse effect; global warming); rural residence (e.g. NOT urban; medically underserved; farmworker); and intervention (e.g. prevention; protective factors), which were then paired with terms representing each of the four main CDC framework sections (increasing CO 2 levels; rising sea levels; extreme weather; and rising temperatures). Pre-identified sentinel articles were also hand-searched for keywords relating to the study objectives. The draft search results were assessed by the team and terms were revised and again tested in PubMed.
The search terms were then translated for each literature database identified as appropriate for the study topic. A total of five bibliographic databases were searched: EBSCO Environment Complete, EBSCO GreenFILE, Embase.com, MEDLINE via PubMed, and Web of Science Classic Core Collection (Science Citation Index Expanded, Social Sciences Citation Index, Arts & Humanities Citation Index, Conference Proceedings Citation Index-Science, Conference Proceedings Citation Index-Social Sciences & Humanities, Book Citation Index-Science, Book Citation Index-Social Sciences & Humanities, Emerging Sources Citation Index, Current Chemical Reactions, Index Chemicus). The EBSCO Environment Complete and EBSCO GreenFILE searches were run simultaneously. All searches were initially undertaken 21 July 2020 and rerun for updates on 1 March 2021. The final screening of all articles was completed on 11 October 2021, with the extraction of data and writing of the manuscript taking place until submission to the journal on 15 August 2022. Full search strategies for each database can be found in the supplementary material.

Study selection
A total of 12 427 studies identified through the database searches were uploaded to EndNote X9 (Clarivate Analytics, PA, USA). Duplicates were manually removed leaving 8300 records. We manually removed an additional 253 records with the following locations in the title: Africa, Australia, Canada, Europe, China, Japan; but not if the title also contained USA, States, African American or African-American. Additionally, 124 Morbidity and Mortality Weekly Report review articles were removed, leaving 7923 records. These were uploaded to the systematic review software Covidence [19]. When the searches were rerun an additional 779 records were uploaded to Covidence.
In the combined 8702 records, 231 additional records were identified by Covidence as duplicates and automatically removed. The title and abstract of the remaining 8471 records were screened by seven independent reviewers (DS, EM, SL, SS, ER, LT, GL). Of these, 8174 were excluded for irrelevancy, leaving 297 eligible for full-text review. During the full-text review, four reviewers (DS, EM, PS, GL) independently evaluated each article. Disagreements between reviewers were resolved by discussion and consensus. An additional 248 articles were excluded that did not meet the inclusion criteria, leaving 49 articles that met all eligibility criteria for inclusion in this study. The review and selection processes for the studies are summarized in the diagram in figure 2.

Quality evaluation
Articles included in this review underwent a quality assessment using the 2018 Mixed Methods Appraisal Tool (MMAT) [20] by seven reviewers (DS, EM, AA, PS, GL, RML, LT). The MMAT tool has been used in multiple systematic reviews, such as ours, that included unique quantitative, qualitative, and mixed-methods research articles [21][22][23][24][25]. The MMAT tool is commonly used to evaluate studies focusing on the acceptability, satisfaction with, or barriers to implementation of interventions in the health literature [26]. The tool can be used to appraise five different study designs (qualitative, randomized controlled, nonrandomized, quantitative descriptive, and mixed methods) and includes 25 criteria and two screening questions [20]. Each article was independently rated by two reviewers with disagreements between reviewers resolved by discussion and consensus. If the pair was unable to reach a consensus, a third reviewer (DS) served as the tiebreaker. The results of the MMAT tool were presented using asterisks that correspond to the total score out of five, with scores closer to five indicating higher quality studies.

Data extraction and synthesis
Data were extracted by five reviewers (DS, EM, GL, RML, LT) with each reviewer assigned between 8 and 14 articles to extract. Data points extracted from each included study were specific location with the U.S., sample size and demographics, the domain from the CDC framework, a brief description of the intervention/policy/simulation reported in the study, study design, health outcome(s), statistical analysis (if any), and confounder assessment. If a reviewer was unsure of which data points to extract from a study, the concern was brought to the larger review group with a final decision made by DS, EM, and LT. Given that this study utilized the CDC Impact of Climate Change on Human Health framework [1] to drive the search process, the interventions were descriptively synthesized based on the domain of the CDC framework to which the study belonged.

Results
Across 49 studies, 34 unique interventions were identified to potentially reduce the negative health effects of climate change on human health in the rural States (table 1). The majority of studies included in this review (n = 40) could be classified using the MMAT tool as quantitative (n = 29), qualitative (n = 6) or mixed-methods (n = 5). Three of the 29 quantitative studies were randomized control trials [27][28][29]. The majority of quantitative studies were either descriptive or quasi-experimental. The remaining nine articles included in this review could not be rated/classified using the MMAT tool based on the responses to the first two screening questions (i.e. response of 'no' or 'cannot tell' to the questions 'are there clear research questions?' and 'do the collected data allow to address the research questions?') [30][31][32][33][34][35][36][37][38]. These studies were primarily policy [35] or programmatic case reports [30,31,34,36] and narrative reviews of current policies [32,37], proposed policies [38], or proposed interventions [33]; however, they were included in the review because they described interventions and policies designed to decrease climate change's impact on rural health.

Summary of interventions by domain
Using the CDC framework domains, eight studies focused on air pollution, six on changes in vector ecology, five on water quality impacts, three on severe weather, two on extreme heat, one on increasing allergens, and one on water and food supply impacts. No interventions focused solely on environmental degradation as these interventions were used across multiple domains. Eight interventions intended to protect human health across multiple domains (table 1). Because unique interventions were used across multiple domains in several studies, the total number of interventions identified is greater than the total number of studies identified.

Air pollution
Eight unique interventions were identified to address air pollution risk in the rural U.S. (table 2). Three of these interventions targeted populations (e.g. schools, communities, counties) [36,39,40] and five interventions targeted individuals [27,[41][42][43][44][45]. For example, one of the population-based interventions Historically, crop rotation used to be more common due to the diversified crops produced in the region. However, 'corn is king' and is now the predominant crop produced. Farmers also discussed the lack of markets for crops other than corn as being a driver for solely producing corn in the region. They also recognized the importance of diverse crop rotations for achieving broader conservation goals. Farmers recognized the importance of crop rotations as a viable mechanism of responding to a changing climate.
The loss of livestock and transition to only 'crop farming' was recognized as a reason for not rotating crops. Farmers also identified the high cost of rented farmland and the need for ensuring profit, which limits the rotation of less profitable crops. * * * * (Continued.) focused on the use of flags to alert populations of air quality risks to minimize exposure to air pollution and supported broader use of low-cost, educational interventions to alert persons to environmental risk [36]. This study [36] along with the findings of Rappold et al [39] support the broader use of low-cost, educational interventions to alert persons to environmental risk stemming from air pollution. At the individual level, two studies replaced old wood burning stoves with newer ones to minimize the pollution from stoves used for heating inside the home [42,45]. These studies found that the use of modernized wood stoves decreased the concentration of fine particulate matter in homes [45] and also decreased odds of wheezing and illness-related school absences [42].

Changes in vector ecology
Six distinct interventions addressed changes in vector ecology (table 2). Five interventions targeted populations (e.g. states, communities, counties) [46], [47][48][49][50], and one targeted individuals [51]. To illustrate, two population-based studies focused on decreasing tick prevalence in high-density rural areas [48,49]. These studies provided evidence that targeting behaviors such as performing tick checks [49], bathing within 2 h of being outdoors, [30] and applying tick collars to family dogs [48] help to reduce the incidence of Lyme disease. The individual-based intervention provided screening and recommendations to pregnant women with confirmed or probable Zika virus infection, which found that their health brigade model of community engagement was successful and should be replicated to successful respond to future infectious disease outbreaks in resource limited settings [51].

Water quality impacts
Five unique population-based interventions were identified across multiple studies [34,37,38,[52][53][54][55][56][57] to improve water quality (table 2). The most common intervention in this group was the implementation of a watershed nutrient management intervention that aimed to regulate nutrients and engage farmers through water monitoring, watershed planning, and outreach efforts by private and public partners [37,38,52,53]. Specifically, the work of Shortle et al [37] problematizes the use of 'the polluter pays' to decrease non-point source agricultural pollution. Their work and the work of Sweeney and Blaine [38] highlight the need for appropriate incentive programs and outreach to tackle non-point source pollution in agricultural communities [37,38]. Another example of an intervention was a community-based intervention that developed the NatureNet technology platform consisting of a website, interactive display, and application to support data sharing and planning for community-driven environmental projects [54].

Severe weather
Three unique interventions were identified to evaluate and implement medical services in response to severe weather events (table 2). Two interventions targeted populations [31,32] while the other intervention provided clinical services to individuals in areas affected by severe weather [58]. For example, one population-based intervention established an emergency shelter for special needs populations who evacuated the Texas coast during Hurricane Gustav [31]. While the primary focus was on evaluating educational outcomes, the authors concluded that interventions that mobilize the skills of academic, practice professions in meeting the needs of communities during disaster response should be supported [31].

Extreme heat
Two interventions were identified to address exposures to extreme heat (table 2). Each of these interventions were implemented at the individual level [28,35]. One Florida-based intervention provided cooling vests and bandanas to agricultural workers during the day to decrease core body temperature, and found that bandanas alone decreased core body temperature compared to control group participants [28]. A Southern California-based labor and occupational safety program trained health promotores in planning and training activities to reduce heat-related illness but did not describe health outcomes related to the training [35].

Increasing allergens
Only one educational intervention was identified that provided education in response to increased allergens [29]. In this study, lay health educators offered asthma and general health education courses to students in second through fifth grade to promote their understanding of asthma. The intervention was successful in increasing knowledge of and self-management of asthma symptoms [29].

Water and food supply impacts
One intervention was identified to address food and water supply at the individual level (table 2). This school-based intervention held activities at various locations (e.g. cafeteria, classroom, community) that were designed to improve diet quality and to increase the intake of traditional foods among two rural, remote Reviewed studies that utilized this intervention Air pollution Air Quality Flag Used flags to represent the colors of the U.S. AQI system to alert school communities of ambient air quality risk for children with asthma. This program evaluation described a community-wide program to influence policy related to ambient air quality and educate about air quality and potential health risks.

Population
Shendell et al [36] Childhood Asthma Project Community health workers trained in environmental assessment conducted a home-visitation program in which they assess homes of migrant children and make recommendations to families on measures that can reduce the children's exposures to environmental triggers that can potentially exacerbate asthma symptoms. A total of eight home visits occurred approximately one month apart from each other. Families were provided education modules that are designed to increase awareness of asthma triggers, asthma care plans, and medication management.

Individual
Postma et al [43] Montana Home Visiting Program for children with asthma A home visiting program was designed to address residential asthma triggers, provide participants with asthma self-management education, and coordinate asthma care in school, childcare, and the clinical setting. Participants received six contacts with a registered nurse to increase asthma control.

Individual
Fernandes et al [41] Nutrition Based Lesson Series (Body Balance Lesson Series) A nine-lesson nutrition-based lesson series, 'Body Balance: Protect Your Body from Pollution with a Healthy Lifestyle' was developed based on a needs-based assessment to enhance the understanding of environmental health and protective actions.

Individual
Brewer et al [27] Salinas Asthma Intervention A multi-site asthma intervention to increase asthma education and treatment/control activities among providers/teachers, the community, and patients/individuals. The intervention focused on training healthcare providers and patients on how to best control asthma symptoms.

Individual
Vogt et al [44] Smoke Forecast Based Intervention Simulation of forecasted-based interventions implemented at county level to reduce personal exposure to populations susceptible to complications from smoke. Interventions took place when a 24 h-ahead or 48 h-ahead smoke forecast predicted PM2.5 concentration exceeding a threshold and the population assumed a level of adherence.

Population
Rappold et al [39] Telemedicine A telemedicine network was implemented to provide remote providers to rural hospitals from a central academic medical center. Such a network allows for remote assessment of patients and helps to reduce the number of patients transported from rural hospitals to urban centers for treatment.

Population
Whetten et al [40] Wood Stove Modernization Older wood stoves used for heating were replaced with new, less-polluting wood stoves in homes using wood stoves for heating.

Individual
Noonan et al [42], Ward et al [45] Changes in vector ecology Deer-Targeted Acaricide Applicator Introduction of baited four-poster acaricide applicators to area of high deer/blacklegged tick population density.

Population
Miller et al [46] (Continued.) West Nile Virus An education and awareness campaign was designed to increase community awareness about West Nile Virus and measures to protect oneself from the virus. Educational materials included news releases (written and video), newsletter articles, public service announcements (newspaper and radio), pre-written letters to editors, mailings to veterinarians, and brochures.

Population
Fox et al [50] Health Communication Central California public health agencies' risk communication on Valley Fever.

Population
Matlock et al [47] Pediatric Health Brigade Pediatric specialists were recruited to provide the recommended evaluations and screenings for children born to mothers with confirmed or probable Zika virus during pregnancy in the US Virgin Islands.

Individual
Godfred-Cato et al [51] Rocky Mountain Spotted Fever Rodeo A program that was enacted to decrease the prevalence of brown dog ticks. The program focused on the systematic registration of homes and dogs, application of dog collars containing insecticide, lawn spraying of insecticide, dog population control via spay-neuter opportunities.

Population
Drexler et al [48] Peridomestic Prevention Measures for Lyme Disease Personal protective measures included landscape features/modifications, personal protection, and chemical control practices.

Population
Connally et al [49] Environmental degradation

See Interventions that Spanned Multiple Domains, below.
Extreme heat Cooling Clothing (i.e. vests and bandanas) Cooling vests or cooling bandanas were provided to agricultural workers during the workday to decrease core body temperature.

Individual
Chicas et al [28] UCLA Labor Occupational Safety and Health Program (LOSH) Specific strategies included community-based outreach, popular education, and organizational capacity building.
Integration of health promotores into core program planning and training activities and the expansion of campaign activities to a wide variety of rural and urban workers.

Individual
Riley et al [35] Increasing allergens Asthma education classes Lay health educators (LHE) offered asthma education/general health promotion classes to elementary school students grades 2 through 5 with the aim of seeing improvements in children's asthma knowledge, asthma self-management, and self-efficacy for managing asthma symptoms.

Individual
Horner et al [29] Severe weather Improvements to Climate Change policy Four key principles to evaluate health policies focused on climate change: mainstreaming, linked approach, population perspective, and coordination.

Population
Ganesh and Smith [32] (Continued.)  [58] Shelters for Medically Complex Persons During Hurricane Emergency sheltering of medical special needs populations evacuated from the Texas coast during Hurricane Gustav.

Population
Deal et al [31] Water and food supply impacts Neqa Elicarvigmun or the Fish-to-School Program A school-based, multilevel intervention that included activities in the cafeteria, classroom, and community was designed to improve diet quality and increase intake of traditional foods. It was evaluated using a pre-and post-comparison group design with data collection occurring at three time points: baseline, four months, and nine months.

Individual
Bersamin et al [59] Water quality impacts 2015 Water Policy and Agreement of the Eastern Snake Plain Aquifer In 2015, Idaho overhauled its water policy and created a water use agreement for farmers located in the region of the Eastern Snake Plain Aquifer. The new legislation had the goal of reducing water consumption from the aquifer by 13% per year.

Population
Running et al [57] Water, Sanitation, and Hygiene Education Programs A team of professionals provided interactive, culturally and literacy appropriate WASH education to target community groups within the school, senior center, and larger community. Arcipowski et al further adapted WASH programs and also provided a clean water kiosk (2017).

Population
Arcipowski et al [56], Lee et al [34] Watershed Nutrient Management Water monitoring, watershed planning, and outreach efforts by private and public partners, including cost-share incentives for farmers, in order to manage nutrients and engage farmers in water quality management.

Population
Enloe et al [52], Sweeney et al [38], Savage and Ribaudo [53], Shortle et al [37] Water filtration system for agricultural drainage. ABSR Facility at Panoche removed 95% of the influent nitrogen load and 80% of the influent selenium load. Recent results from the ABSR Facility including DAF and slow sand filter units indicated that removals of 90% or greater are possible. Average total soluble selenium mass removal of >76% was achieved.

Population
Green et al [55] NatureNet technology platform to support the CDEPs ('community-driven environmental projects') NatureNet consisted of a website, an interactive display in a community center and for use in WSA classes and on computers at home, and iOS and Android mobile 'apps' that supported collection of data and community interaction for CDEPs. Options to 'Explore' , go to 'Projects,' submit 'Design Ideas' to help tailor the software, go to the 'Communities' page, and submit 'Contributions' . Also includes likes and comments, maps, members can store data, notes, or project plans.

Population
Preece et al [54] (Continued.) Crop Rotations Farmer used diversified rotations that include small grains, forages, or other crops on land they own and/or rent (other than corn).

Population
Roesch-McNally et al [67] Deliberation with Analysis Deliberation with analysis model of public participation conducted during community meetings with the purpose of building community resilience and ability to adapt to climate change in Marquette County, Michigan.

Population
Arnold et al 2020 Farm Worker Family Health Program (FWFHP) Students and faculty members from departments of nursing, physical therapy, dental hygiene, and psychology worked as an interdisciplinary team for two weeks to deliver health care services to 500 migrant farm workers and 500 migrant children.

Population
Connor et al [30] Participatory Action Research Participatory action research methods aimed to empower community members and involve them in the systematic design of projects to impact the planning, response, and recovery from various climate related health disasters and health effects.

Population
Miller-Hesed et al [69], Gibson et al [33], Laursen et al [70], Thomas et al [75], Tovar-Aguilar et al [71] Planning Support System Models or information systems designed to help local governments and other organizations plan various programs to help communities adapt and mitigate the impacts of climate change on health.

Population
Muller and Yin [72], Greenberg et al [73] Rural Coastal Community Resilience (RCCR) framework Framework implemented into rural coastal communities to analyze their level of vulnerability or resilience to climate change effects. Administered questionnaires to participants and held discussions among participants regarding the following themes: livelihood dependency and livelihood diversity, poverty and prosperity, unsustainable development and sustainable development, community disengagement and community cohesion, and rigidity and agency. RCCR framework intended to boost resilience by stimulating dialogue between community members, resource managers, planners, and other stakeholders necessary to maintain their ways of life, subsequently promoting future implementations of intervention and climate change planning strategies.
Population Jurjonas et al [74] Indigenous communities located within Alaska [59]. This intervention successfully increased diet quality and fish intake in school-aged, Alaskan Native, children [59].

Multiple domains
Eight interventions were identified to address issues that encompassed multiple CDC domains (table 2). Four interventions established crisis counseling and psychiatric programs for mental health needs of individuals following a natural disaster [60][61][62][63]. Seven of these unique interventions encompassing multiple domains were conducted at the population level [30,33,[64][65][66][67][68][69][70][71][72][73][74][75]. One example of an intervention spanning multiple domains is the Farmworker Family Health Program, [30] which serves migrant farmworkers in the Southeastern US in an attempt to decrease multiple negative health impacts related to extreme heat and changes in vector ecology. The program also highlights the importance of community collaborations when providing innovative clinical services and the need to meet the community where they stand [30]. In five studies, participatory action research was used to engage and mobilize community members on the planning, response, and recovery from various climate-related disasters in Hawaii, [70] Maryland, [69] and more broadly, across the U.S. [33] as well as to improve water quality on tribal lands, [75] and the use of personal protection equipment in citrus growers in Florida [71].

Quality appraisal
Using the MMAT, most articles included in this review were rated as high quality. The majority of quantitative studies received ratings of four or five stars, out of a possible five stars (table 1). Only five studies received ratings of three stars or less. Most of the qualitative studies received high ratings on the MMAT. Only one qualitative study did not receive five stars due to flaws in the data collection methods and analysis of the qualitative data [54]. Similarly, mixed-methods studies included in this review were generally rated as high quality (either four or five stars). Only one study received a rating of one out of five stars because the authors used a mixed-methods design but never presented the qualitative findings [44].

Discussion
This systematic review details the existing interventions that have been developed to decrease the impact of climate change on rural health outcomes in the United States. Across 49 articles, published from 2003 to 2021, 34 unique interventions were described. Overall, there is a lack of high-quality, randomized controlled trials that aim to evaluate the effect of interventions, and lack of interventions to address the health consequences of severe weather, heat stress, increasing allergens, and environmental degradation. Given the impending, severe consequences of climate change, we expected more research would have been published over the past decades since the IPCC report was published in 1988. In fact, across major databases we searched, the first intervention-based article we were able to retrieve was published in 2003. However, in this discussion, we suggest that despite the lack of published academic research, health interventions are likely being conducted at the grassroots level and not published in the peer-reviewed literature. Our review only identified three randomized controlled trials, with two of these three published in the last five years [27,28]. This is highly concerning given that randomized controlled trials are considered the gold standard for establishing causality and proof of concept. However, it would not be ethical to conduct randomized control trials if there is not equipoise, or a state of uncertainty about an intervention's efficacy, given the concerns about intentional withholding of potentially beneficial programs among those randomized to a control group [76]. Furthermore, many climate-related health-affecting events cannot be randomized (e.g. severe weather events). Randomized control trials are also resource intensive. However, with the WHO predicting less than ten years to act on climate [77], researchers must consider the urgency to provide solutions. Despite the lack of randomized controlled trials, original research on climate change's impact on health has increased 11-fold from 2007 to 2020 [78]. This is consistent with our review: despite searching for articles published as early as 1988 in our search criteria, we only found one article published before 2007 [73]. Even with the recent surge in research, there is still a dire need for time-efficient and high-quality scholarship (e.g. systematic program evaluations and epidemiological studies, such as retrospective cohort studies) that investigates intervention efficacy and effectiveness for reducing the impacts of climate change on human health.
While we expected to have found more research conducted in rural US areas, there may be a dissociation between what is being done on the local, programmatic level and what is being investigated through an academic lens. It has been suggested that the efforts of grassroots organizations that are implementing strategies to reduce the burden of climate-related impacts on health do not intersect with traditional biomedical and academic scholarship [78][79][80][81]. It is highly possible that this is one reason why we did not find as much research as expected in this review. There are many grassroots organizations throughout the US that are committed to combating the effects of climate change on their communities. For example, the Women's Earth and Climate Action Network, International (WECAN), supports many grassroots efforts to promote a sustainable environment in a changing climate [82]. In the Gulf South, WECAN supports the Okla Hina Ikhish Holo: People of the Sacred Medicine Trail. This effort is described as 'a network of femme and non-binary Indigenous gardeners growing Food Sovereignty in the Gulf South' [83]. However, mistrust felt by grassroots organizations, and hesitancy to partner with academic institutions is not unfounded. Many research universities have a history of contentious, exploitative relationships with the communities in which they exist [84][85][86]. It is the responsibility of these institutions to establish community partnerships centered on the needs of communities and their priorities related to protecting their health in a changing climate.
Interestingly, in this review, participatory action research, also known as community-based participatory research, was frequently used as an intervention across multiple studies reviewed [33,[69][70][71]75]. Participatory action research is traditionally thought of as a research method. However, the use of this method as an intervention can mobilize communities to tackle issues related to climate change. This is encouraging because engaged community members have been effective in reducing health inequities [87]. Co-creating research plans, data collection, analysis and interpretation with engaged community members are key to addressing complex problems like climate change [87]. A possible explanation for the popularity of this design could also be the 'bottom-up' approach to climate change mitigation through grassroots movements [88]. It is exciting to have found examples of academic-community partnerships tackling climate change's impact on rural health. However, there is still a pressing need to conduct high-quality, community-based research in rural areas of the US to evaluate interventions, programs, and policies designed to decrease climate change's impact on rural health. Academic scholars may gain important insights from the participatory action research articles included in this review.
Although using community-based participatory action research design could reduce the health burden of climate change, this method is time-consuming, and requires a long-term commitment from research team members and community members. Climate mitigation is time sensitive. Van Aalst et al [88] suggest building on pre-existing community risk assessments performed by governmental agencies or community organizations. In rural communities, focusing on climate-related disease burdens in crop and livestock workers and those working in forestry and fishing industries would likely develop interventions transferable to other populations within rural areas.
A surprising finding from this review were the few articles published on interventions to protect against the health effects of extreme heat on rural populations. Confirmed by another systematic review on climate change health interventions, there appears to be a gap in what is known about the health effects of heat stress, and what is being done about it [16]. It was promising that the two articles from this review focused on outdoor workers [28,35], including farmworkers, a group that is extremely vulnerable to heat-related illnesses [6,89]. However, no studies were identified that focused on other vulnerable groups to heat-related illnesses, such as rural older adults who live in areas that lack indoor cooling during extreme heat events [90]. Another gap found in this review was the lack of interventions related to protecting rural population health from severe weather patterns leading to droughts and water shortages, both of which are increasing due to climate change [77]. Developing, implementing, and investigating the effectiveness of interventions designed to protect rural populations who will experience water scarcity is a priority area for future research. This review did identify four studies focused on improving health outcomes after hurricanes in rural areas [31,33,58,63]. Hurricane intensity is an exceptionally challenging climate event for rural, vulnerable populations throughout the southeastern United States. There are approximately 60 million persons living in the Atlantic and Gulf of Mexico regions of the United States [91] and many in these regions live within low-lying areas along the coast [11]. Of these four studies, only two were able to be methodologically rated for quality in this review [58,63], further showing the need for timely, high-quality scholarship that explicitly evaluates the impact that interventions have on extreme weather events.
Three policy studies included in this review focused on cap-and-trade programs, in which emitters of pollution are charged for their emissions either through taxes or through tradable means, such as permits and allowances [92]. While these programs were enacted at the state level in California [64], New York [65], and Ohio [66], they non-selectively impact both rural and urban populations within a state. Even though interventions should be tailored to the unique needs of rural areas, rural areas will still benefit from interventions that non-selectively focus on decreasing the impact of climate change on health across rural and urban populations. It is worth noting that not all cap-and-trade policies have been successful. The cap-and-trade programs in California and New York were successful in reducing emissions of carbon dioxide (CO 2 ), [64] methane (CH 4 ), [64] nitrous oxide (N 2 O), [64] fluorinated greenhouse gases [65] and nitrous oxides (NO x ) [65], respectively. Ohio's cap-and-trade program was not successful in supporting farmers' uptake of conservation practices to reduce non-point source agricultural pollution [66]. Investigating the reasons behind cap-and-trade success and the factors influencing their impact on climate change's impact on rural health areas remains an area of further investigation.

Resources for climate change researchers
For future studies on the effect of climate change on human health research, a One Health approach should be employed. The One Health approach is holistic and stems from an ecosystem approach to thinking about human health that recognizes the inherent linkage between the environment, human health, animal health, and the social context in which all living beings live [93]. Many of the articles included in this review that focused on water quality were included due to the linkage between water quality and human health, even when the article did not explicitly measure health outcomes related to herbicides and/or pesticides used in rural crops that were present in drinking water. For example, one article focused on improving the management of animal manure produced and used as fertilizers [53]. Because farmers have had to grow more food on less arable land, there has been an uptick in fertilizer use in agriculture [94]. Increased food production, land-use change, and fertilizer use, particularly of nitrogen-based fertilizers, has accelerated climate change and has multiple impacts on the environment and human health through groundwater contamination [95,96]. Researchers working to understand the impacts of climate change on human health are encouraged to consider the concept of One Health when designing and conducting studies.
Researchers could also refer to the National Institute of Health (NIH)'s Climate Change and Health Initiative to further understand the needs for climate change and health research. Seven of NIH's institutes and centers are working together to address the climate crisis through research with 'urgency, foresight, innovation, and collaborative spirit' (p 7) [97]. Some of the research needs included in the Initiatives' Strategic Framework are climate change's effect on mental health and food quality. Interestingly, another research need highlighted was protecting vulnerable populations from the impacts of extreme temperatures, especially heat in urban settings. Literature and results presented in this review suggest there is a great need for heat-health research in rural settings, as well.

Strengths and limitations
To our knowledge this is the first review to specifically investigate interventions conducted in the rural US to reduce the impacts of climate change on human health. The use of the CDC 'Impact of Climate Change on Human Health' framework highlights the broad range of academic disciplines that have worked across the framework's eight domains to better understand how to protect human health due to a changing climate. Our broad research question, and the narrow focus on specific interventions, limited our ability to perform a meta-analysis of clusters of interventions on human health outcomes. In order to quantify the impacts, future reviews will need more precise research questions that can be compared within domains and focus on a specific health outcome of choice. We did not review the gray literature, which may have limited our results to academically published articles describing interventions related to climate change on health. Future reviews may find gray literature to be a rich source of information about local actions to protect health due to a changing climate.

Conclusion
Several studies have been published on health interventions to reduce the health impacts of climate change effects onf air pollution, vector ecology, and water quality on the rural US population. There is a need for high-quality, timely scholarship to implement and evaluate efficacy and effectiveness of health interventions, as well as interventions to combat severe weather, heat stress, increasing allergens, and environmental degradation. Our review highlights some specific gaps in health research in rural spaces. Effective interventions that target the health of rural Americans must be prioritized as climate change continues to impact human mobility and mortality.

Data availability statement
All data that support the findings of this study are included within the article (and any supplementary information files).

Funding
This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.