*177 OPINION

On June 28, 2002, eleven farmers and farms from Appomattox County, Virginia (collectively “the Farmers”) filed suit against Appomattox County, the County Board of Supervisors, and the County Administrator (collectively “the County”) to challenge two County ordinances that relate to the use of biosolids. 1 The District Court for the Western District of Virginia issued a preliminary injunction against the County prohibiting it from enforcing the biosolids ordinances. The County appeals to this Court from the entry of the injunction order, maintaining that it should be vacated. As explained below, the District Court did not abuse its discretion, and we affirm.

I.

The Farmers are all either residents of Appomattox County who engage in farming activities or business entities that own or lease farmland in Appomattox County. In the summer of 2001, the Farmers began a lengthy permitting process with the Virginia Department of Health (“VDH”) to obtain permits to apply biosolids to their farmland. The Farmers provided detañed information to VDH about their fields, soñs, and proposed use of biosolids in two separate applications. VDH provided this information to the County and the County requested some changes in the proposed use of biosolids, which were accommodated. Permits for land application of biosolids on the Farmers’ land were issued on March 29, 2002.

Beginning September 4, 2001, the County held a number of public hearings regarding the possibility of regulating the land application of biosolids. On February 4, 2002, and March 18, 2002, the County Board of Supervisors adopted two ordinances that restricted and regulated land application of biosolids. Despite the existence of the permits, the Farmers añeged that the County’s ordinances effectively prohibited the application of biosolids and they filed this lawsuit.

On July 15, 2002, the Farmers sought a preliminary injunction barring the County from implementing or enforcing ordinances that interfere with land application of biosolids in Appomattox County. At the evidentiary hearing before the District Court on July 30, 2002, the Farmers presented three witnesses and six exhibits in support of the preliminary injunction motion. The County cross-examined the Farmers’ witnesses and submitted two exhibits. On August 2, 2002, the District Court issued an opinion granting in part and denying in part the Farmers’ motion for a preliminary injunction. O’Brien v. Appomattox County, 213 F.Supp.2d 627 (W.D.Va. Aug.2, 2002). In its memorandum opinion, the District Court enjoined and prohibited the County from enforcing the biosolids ordinances with regard to the named plaintiffs, but afiowed a number of general restrictions on the land application of biosolids to remain in effect.

The County filed a timely notice of appeal.

II.

This Court reviews the grant or denial of a preliminary injunction for abuse of discretion, recognizing that preliminary injunctions are “extraordinary remedies in *178 volving the exercise of very far-reaching power to be granted only sparingly and in limited circumstances.” MicroStrategy, Inc. v. Motorola, Inc., 245 F.3d 335, 339 (4th Cir. 2001) (internal quotation marks omitted). We accept the District Court’s findings of fact absent clear error, but review its legal conclusions de novo. Giovani Carandolo, Ltd. v. Bason, 303 F.3d 507, 511 (4th Cir. 2002). This standard is “not a rule of perfunctory appellate review but one of careful scrutiny.” Direx Israel, Ltd. v. Breakthrough Med. Corp., 952 F.2d 802, 815 (4th Cir. 1991).

III.

In this Circuit, the entry of a preliminary injunction is governed by the four-part test set forth in Blackwelder Furniture Co. of Statesville, Inc. v. Seilig Mfg. Co., Inc., 550 F.2d 189 (4th Cir. 1977). The four Blackwelder factors are: (1) the likelihood of irreparable harm to the plaintiff if the preliminary injunction is denied, (2) the likelihood of harm to the defendant if the requested relief is granted, (3) the likelihood that the plaintiff will succeed on the merits, and (4) the public interest. Rum Creek Coal Sales, Inc. v. Caperton, 926 F.2d 353, 359 (4th Cir. 1991) (internal quotation marks omitted).

In applying Blackwelder, a court must first “balance the likelihood of irreparable harm to the plaintiff against the likelihood of harm to the defendant.” MicroStrategy, Inc., 245 F.3d at 339 (quoting Blackwelder, 550 F.2d at 195). If this balance of hardships “tips decidedly in favor of the plaintiff,” Rum Creek Coal Sales, 926 F.2d at 359, then it will typically “be enough that the plaintiff has raised questions going to the merits so serious, substantial, difficult and doubtful, as to make them fair ground for litigation and thus for more deliberate investigation.” Blackwelder, 550 F.2d at 195 (internal quotation marks omitted). But if the balance of hardships is substantially equal between the plaintiff and defendant, then “the probability of success begins to assume real significance, and interim relief is more likely to require a clear showing of a likelihood of success.” Direx, 952 F.2d at 808 (internal quotation marks omitted).

In its memorandum opinion, the District Court found that the Farmers “will suffer immediate, significant, and acute irreparable harms if their motion for an injunction is denied.” Tommy O’Brien, et al. v. Appomattox County, Virginia, et al., Civ. No. 6:02-0043 (W.D.Va. August 2, 2002) (J.A. 510). First, without preliminary relief, the Farmers would suffer economic losses that they may or may not be able to recover through pending litigation. These economic losses include lost profits from reduced crop yields and the expense of replacing biosolids, which are free, with commercial fertilizers. Second, an injury to the environment from the increased use of chemical fertilizers would accompany a ban on biosolids. And third, the Farmers would be forced to delay the potential long-term benefits to the soil that biosolids may provide.

The County argues that granting the preliminary injunction motion will cause them certain, irreparable harms. Specifically, the County argues that citizens of Appomattox County will be exposed to strong and offensive odors associated with the application of biosolids. Further, the County cites possible adverse health effects associated with biosolid use. The District Court weighed these concerns and determined that “instead of suffering any immediate, irreparable harm, [the County] only facets] the potential for uncertain, future injuries — the fear of possible, adverse health effects.” Tommy O’Brien, et al. v. Appomattox County, Virginia, 213 F.Supp.2d 627 (W.D.Va. 2002) (J.A. 510). Applying the first two factors of the Blackwelder analysis, the District Court determined that the County’s pro *179 spective fears are not as certain, identifiable, or as severe as the damages claimed by the Farmers and that the balance tips strongly in the Farmers’ favor. In light of the widespread use of biosofids in Virginia and elsewhere in the United States, the regulations and examinations undertaken by the Virginia General Assembly and the United States Environmental Protection Agency (“U.S.EPA”), and the studies by the scientific community, the fear of possible, adverse health effects is too attenuated at this time to outweigh the likelihood of harm to the Farmers. We therefore conclude that in balancing these potential hardships, the District Court did not err in finding that the balance tipped “strongly” in favor of the Farmers.

Having established that the balance of hardships clearly weighed in favor of the Farmers, the next question is the Farmers’ likelihood of success on the merits. Pursuant to the law in this Circuit, if the balance of harm tips strongly in favor of the plaintiff, a preliminary injunction will be granted “if the plaintiff has raised questions going to the merits so serious, substantial, difficult and doubtful, as to make them fair ground for litigation and thus for more deliberate investigation.” Rum Creek Coal Sales, 926 F.2d at 359. In other words, the plaintiffs case must present a “substantial question.” In its memorandum opinion, the District Court reviewed the Virginia Supreme Court’s decision in Blanton v. Amelia County, 2 the legislation enacted by the Virginia General Assembly limiting the role of counties in regulating biosofids, and the effect of these ordinances on land-application of biosofids. In fight of the recent decisions by the Virginia Supreme Court and the Virginia General Assembly, we cannot conclude that the District Court erred in determining that the claims and evidence provided by the Farmers raise such serious, substantial, and difficult issues that they warrant more deliberate investigation.

Finally, the District Court determined that because the VDH and the U.S. EPA currently regulate the land-application of biosofids and will continue to do so during the pendency of this litigation, the public interest favors the granting of the injunction until a determination on the merits can be completed. We conclude that the District Court did not abuse its discretion in reaching this conclusion.

rv.

Having reviewed the record, the parties’ briefs, and the Blackwelder factors, and having had the benefit of oral argument, we conclude that the District Court did not abuse its discretion in awarding the Farmers the preliminary injunction against the County. Accordingly, we affirm.

AFFIRMED.